Federal vs State Firearms Law: Two Layers, One Set of Rules

The comparison between federal and state firearms law begins with a practical question rather than an abstract one. A purchaser at a licensed dealer’s counter, a carrier preparing to cross a state line, a student opening a statute book for the first time, and a resident of a city that maintains an ordinance of its own all confront versions of the same underlying problem. Each asks, in a different setting, which law applies to a particular purchase, a particular journey, a particular act of possession, or a particular address. The question sounds simple, and the structure that answers it is orderly, but the answer rarely comes from a single source. Two layers of law operate at the same time, each written by a different legislature, each enforced through its own institutions, and each capable of imposing a condition that the other layer does not impose. A third layer, the law of a city or county, enters the picture in some places and adds a further question about the relationship between local rules and the state law above them.

Formally, the comparison has a precise identity. On one side stands the federal framework, chapter 44 of title 18 of the United States Code, a body of law built on the Gun Control Act of 1968 and administered largely through licensees, the federally licensed manufacturers, importers, and dealers who form the commercial channel through which firearms move in commerce. On the other side stand the firearms statutes of the fifty states and the District of Columbia, fifty one separate bodies of law, each enacted by its own legislature and each reflecting its own choices about permits, transfers, carrying, storage, and the categories of firearms and persons that its law addresses. The federal side is a single system, uniform in text across the country. The state side is a collection of systems, similar in architecture from state to state yet different in detail at almost every point where a legislature has exercised the choices open to it.

One point requires plain statement at the outset. This article is general information about the structure of firearms law in the United States; it is not legal advice, and it states no reader’s obligations under the law of any state. The discussion that follows describes how the federal system and the systems of the states are organized, what each layer does, and how the layers relate to one another as a matter of legal structure. It identifies mechanisms, institutions, and categories. It does not tell any purchaser, carrier, dealer, student, or resident what that person must do, may do, or must refrain from doing in any particular state or locality, because obligations of that kind depend on the law of the jurisdiction concerned and on facts specific to the individual case.

The federal layer, stated plainly, does three things. First, it licenses the commercial channel: the manufacture, importation, and sale of firearms as a business take place through holders of federal firearms licenses, and transfers by those licensees follow federally prescribed procedures. Second, it defines prohibited persons: categories of individuals to whom firearms may not be sold or transferred and who may not lawfully receive or possess them under federal law, whatever the law of the state of residence may separately provide. Third, it regulates interstate movement: the transfer of firearms across state lines, the sale by a licensee to a resident of another state, and the transport of a firearm through states where possession would otherwise raise a question all bear a federal imprint. Beyond those three functions, the federal layer is comparatively contained. Federal law enacted no general system of purchase permits for individuals, no general federal licensing of owners, and no general federal mandate governing storage inside a home. The subjects that dominate the daily experience of owners and purchasers (permits, carrying, storage, and the detailed conditions on private transfers) belong predominantly to the states’ layer, and the federal framework was constructed on the assumption that the law of the states on the same subjects would continue to operate beside it.

Who licenses a firearms dealer?

A firearms dealer is licensed by the federal government under section 923 of title 18. The same federal licensing system covers manufacturers and importers, and a dealer holds a federal firearms license in addition to any separate state dealer license that a minority of states required in 2021 under their own statutes.

The licensing provision, section 923 of title 18, conditions the federal license on statutory criteria and places the licensee inside a regime of record keeping and inspection. When a licensee transfers a firearm, the transfer requires a completed transaction record, Form 4473, and a background check through the National Instant Criminal Background Check System, the federal check prescribed by section 922(t) of title 18. Licensees keep the records of their transfers, and those retained records form the documentary spine of the federal system: a firearm that passed through the commercial channel left a record at the licensee that sold it, even though no federal registry of owners arises from the arrangement. A fuller account of the statute that built this structure appears in the Gun Control Act of 1968 complete guide. The point for the comparison is one of location. The requirement that a dealer be licensed, that a form be completed, and that a check be run before a licensee transfer comes from the federal layer in every state alike. Whether a purchaser must also hold a permit under the law of the states before the transaction begins, and whether a period of waiting under the law of the states follows the federal check, are questions the states’ layer answers separately.

The second federal function, the definition of prohibited persons, supplies the other half of the federal baseline. Section 922(g) of title 18 sets out nine federal categories. The categories cover a person convicted of a felony; a fugitive from justice; an unlawful user of a controlled substance; a person adjudicated as a mental defective or committed to a mental institution; certain persons in immigration statuses defined by the statute; a person discharged from the armed forces under dishonorable conditions; a person who has renounced United States citizenship; a person subject to a qualifying protection order, under section 922(g)(8); and a person convicted of a misdemeanor crime of domestic violence, under section 922(g)(9). A related provision, section 922(n), addresses persons under indictment. The federal categories operate as a national floor of disqualification: a person inside one of the categories faces a federal prohibition in every state, and a licensee may not complete a transfer to such a person in any jurisdiction. The background check at the dealer’s counter exists largely to test a prospective transferee against these categories.

The floor character of the federal categories matters because states may add categories of their own. A state may disqualify additional classes of persons under its own law, may attach its prohibition to additional offenses, and may define the duration and restoration of disqualifications under the law of the states by its own rules. The result is a two part inquiry at any transaction. The federal categories ask whether federal law bars the transfer or the possession anywhere in the country. The state categories ask whether the law of the state where the transaction or the possession occurs imposes a further bar of its own. A negative answer to the first question does not settle the second, and a state cannot subtract from the federal list: possession barred by an unrelieved federal category remains barred by federal law regardless of the state’s position. The prohibited person provisions therefore illustrate the general relationship between the layers in miniature. Federal law draws a line that applies everywhere; the law of the states may draw the line in a different place for purposes of the states; and conduct must satisfy both lines at once.

Interstate movement is the third federal function, and it explains why a purely local understanding of firearms law fails. Section 922(a)(3) and section 922(a)(5) of title 18 bar, with narrow exceptions, the acquisition and transfer of firearms across state lines between persons who are not licensees; the exceptions include bequests and intestate succession and temporary loans for sporting purposes. Within the licensee channel, section 922(b)(3) governs sales to residents of another state: a licensee may sell a long gun to an out of state buyer in a face to face transaction only if the sale complies with the laws of both states, while a handgun may be transferred only to a resident of the licensee’s own state, so that an interstate handgun purchase travels through a licensee in the buyer’s home state instead. The pattern is consistent. Federal law channels interstate commerce in firearms through licensees, treats the buyer’s home state law as part of the governing law of an interstate sale, and leaves intrastate private conduct largely to the states.

The states’ layer, stated plainly, does the work that governs conduct. States decide whether an individual needs a permit or license to purchase a firearm and whether a background check requirement reaches transfers between private parties or attaches only to licensee sales. States decide how firearms may be carried, openly or concealed, with a permit or without one, and states set the qualifications for any carry permit their law provides. States govern storage, including whether a firearm not in use must be secured and what duties arise when a child might gain access. States define categories, specifying which firearms or magazines fall under additional conditions or prohibitions within their borders, in definitions that differ from the definitions of neighboring states. States also supply protective order procedures: the machinery by which a court order translates into surrender of firearms already held, proof of compliance, and retrieval when an order expires. None of these subjects receives comprehensive treatment in chapter 44. Each belongs, in the ordinary run of American practice, to legislatures of the states, and the differences among the codes of the states on each subject form the largest part of the practical variation that the comparison exists to explain.

The contrast between the layers sharpens on the subject of storage. Federal law enacted no general home storage mandate. A narrower federal provision, section 922(z) of title 18, added by the Child Safety Lock Act of 2005 as part of Public Law 109-92, requires a licensee to provide a secure gun storage or safety device with each handgun sale, delivery, or transfer, subject to statutory exceptions. The federal rule attaches to the licensee and to the moment of transfer; it does not prescribe how an owner secures a firearm in a residence afterward. Storage duties beyond that point are the law of the states, and states have answered the storage question in markedly different forms, ranging from a general duty to secure firearms not in use or under the owner’s control to child access prevention laws of varying structure and to codes that penalize access only after an incident or not at all. Protective orders show the same division: the federal prohibitions in section 922(g)(8) and section 922(g)(9) define who may not possess a firearm, but federal law enacted no procedure requiring a prohibited person to surrender firearms already held, and states supply that machinery.

Both layers govern at once because of a principle that sits inside chapter 44 itself. The relationship between federal and state firearms law is not an accident of overlapping drafting, and it is not resolved by asking which legislature acted later or which code reads more comprehensively. Congress addressed the relationship expressly when the modern federal framework was built, and the provision that does the work is section 927 of title 18. That section states the floor principle: federal firearms law under chapter 44 operates as a floor beneath state law rather than as a ceiling above it, and state law on the same subject continues in force alongside the federal provision. The Gun Control Act regulated a national commercial market and set national disqualifications, while legislatures in the states retained authority over the conduct of purchase, possession, and carrying within their own territory. A resident therefore lives under two codes simultaneously, not under whichever code an individual prefers and not under whichever code happens to be encountered first.

Section 927 deserves statement in its own terms. The provision declares that no provision of chapter 44 is to be construed as indicating an intent on the part of Congress to occupy the field in which the provision operates, to the exclusion of state law on the same subject, unless there is a direct and positive conflict between the federal provision and state law so that the two cannot be reconciled or consistently stand together. Congress added the provision through Public Law 90-351 in 1968, and Public Law 90-618 amended it in the legislation that gave chapter 44 its modern form. Every element of the sentence carries weight. The provision speaks to construction: it instructs courts how to read the rest of chapter 44 when a state law on the same subject also exists. The provision disclaims occupation of the field: the mere fact that Congress has legislated on a subject does not push state law out of that subject. And the provision preserves a single narrow opening, the case of a direct and positive conflict, in which the federal and state commands cannot be reconciled or consistently stand together. Outside that narrow case, the design holds: the state law stands, the federal law stands, and both apply to the conduct within their reach.

A direct and positive conflict, in practice, means something far narrower than disagreement, difference, or additional regulation. Two laws conflict in the sense section 927 contemplates when obedience to one requires violation of the other, when the commands point in opposite directions on the same act so that a person or a licensee cannot comply with both at the same time. A state law that adds a condition (a permit before purchase, a period of waiting after the federal check, an additional disqualification under state law) does not create such a conflict, because compliance with both laws remains entirely possible: the transaction simply satisfies the federal requirements and the state requirements in sequence. A state may therefore forbid or condition what federal law merely permits. Federal law may permit a licensee to transfer a firearm after a completed check; a state may nonetheless condition that same transfer on a state permit, and the permission and the condition coexist without contradiction. The consequence for conduct is straightforward. Both layers bind at once, and the applicable rule that governs a transaction in practice is the rule that determines whether the transaction may proceed once every binding condition from each layer has been met.

One distinction completes the account of section 927, and confusion between its two halves has distorted many summaries of the floor principle. Section 927 negates field occupation rather than conflict preemption. Field occupation, sometimes called field preemption, is the doctrine under which federal legislation on a subject displaces state law on that subject altogether, on the reasoning that Congress intended the federal scheme to be the only law in the field. Section 927 forecloses that reasoning for chapter 44: displacement does not follow from the existence or the detail of the federal scheme. Conflict preemption is a different doctrine, under which a particular state law falls because compliance with both the state law and a federal command is impossible in the particular case. Section 927 leaves that doctrine intact, and federal law can preempt a state law where the state law makes compliance with federal law impossible. The rare federal displacements of state law that chapter 44 contains arrive by express provision rather than by implication, as with the interstate transport protection of section 926A of title 18, under which a person not otherwise prohibited may transport a firearm between two places where possession is lawful, notwithstanding state or local law along the route, if the firearm is unloaded and neither the firearm nor its ammunition is readily accessible. Displacement, where the federal framework produces it, is specific and textual, not general and inferred.

The floor principle explains the shape of every later part of the comparison. Because the federal layer is a floor, the meaningful variation in American firearms law sits in the codes of the states: the presence or absence of a purchase permit, the reach of a background check requirement into private transfers, the model of carry the states adopt, the storage duty the states impose, the categories the states define, and the procedures the states build around protective orders. Because both layers bind at once, a change in one layer does not rewrite the other: a federal amendment to chapter 44 leaves permits and storage duties of the states untouched, and a repeal by one of the states of a condition leaves the federal license, the federal form, the federal check, and the federal prohibited person categories exactly where federal law placed them. The opening answer can be given in a single sentence. The federal layer licenses commerce and disqualifies defined persons across the whole country, the states’ layer governs conduct within its borders, and a reader of either code alone holds only half of the applicable law.

The Purchase: Where the State Layer Decides

A purchase is the point at which the division of labor between the federal layer and the states’ layer becomes easiest to see, because a single transaction could pass through both layers in sequence. The federal layer governed the commercial channel through which firearms moved in trade. The states’ layer governed the conditions under which a particular person in a particular place could take a firearm home. A purchaser who dealt with a licensed dealer encountered the federal machinery in every transaction, and then encountered whatever additional machinery the state of the transaction had built around that federal core. A purchaser who dealt with a private seller encountered a different arrangement, one in which the federal check fell away for a transfer within a state and in which the law of the states alone decided whether a check, a permit, or neither stood between the parties. Federal law supplied a uniform baseline for licensed commerce, built on a license for the seller, a record of the transaction, and a check of the buyer. The law of the states supplied the variation, in the form of purchase permits, waiting periods, rules for private transfers, and administrative arrangements that determined which government office actually ran the federal check.

The federal baseline at a licensed dealer rested on three elements, each grounded in chapter 44 of title 18 of the United States Code. Section 923 required manufacturers, importers, and dealers to hold federal firearms licenses, so the commercial channel itself was a licensed channel, entered only by persons whom federal law had authorized to engage in the business. Section 922(t) attached the checking duty to that channel. A licensee transfer required a completed transaction record, Form 4473, and a check through the National Instant Criminal Background Check System before the firearm changed hands, and licensees kept the records of their transactions. The check tested the buyer against the federal prohibitions on possession, the categories of persons whom section 922(g) barred from receiving or possessing firearms, together with persons under indictment, whom section 922(n) barred from receiving firearms in the circumstances that provision described. The same license requirement governed the dealer, the same form documented the sale, and the same federal check screened the buyer, without regard to the state in which the dealership stood. Whether a buyer needed permission obtained in advance, and whether a buyer had to wait after the check before taking delivery, were matters the federal baseline left to the second layer.

Which law decides whether a permit is needed to buy a handgun?

The law of the states decides. Federal law required a background check and a transaction record for a sale by a licensed dealer in every state, and federal law required no purchase permit. A permit to purchase existed only where state law created one, under conditions set by that state alone.

The permit question illustrates the floor principle on which the combined system rested. Section 927 of title 18 provided that no provision of chapter 44 was to be construed as indicating an intent on the part of Congress to occupy the field in which the provision operated, to the exclusion of state law on the same subject, unless a direct and positive conflict existed so that the two could not be reconciled or consistently stand together. A purchase permit created no such conflict. A state that required a permit conditioned a transaction that federal law, standing alone, permitted after a check, and the two layers bound the buyer at once. A state that required no permit left the federal baseline as the whole of the checking structure for a dealer sale.

A purchase permit differed from the federal check in timing and in kind. The federal check was an event at the point of sale, a query run when the buyer stood at the counter of a licensed dealer. A purchase permit was a credential obtained before the sale, secured in advance of any particular transaction and then presented or relied upon when a purchase took place. The check asked whether a named buyer was federally prohibited at the moment of the transfer. The permit system asked a prior question, whether the state had granted the person standing permission to enter the market as a buyer at all. Some systems of the states applied the permit requirement to handguns alone, and some applied the requirement to all firearms. Either way, a buyer in a permit state completed two screenings, separated in time, where a buyer in a state without a permit completed the federal screening alone.

The geography of the purchase permit at the opening of 2021 was compact enough to name in full. A count published by the Johns Hopkins Center for Gun Policy and Research in 2020 listed nine states, Connecticut, Hawaii, Illinois, Iowa, Maryland, Massachusetts, New Jersey, New York, and North Carolina, and the District of Columbia requiring a license or permit to purchase at least handguns, some of them for all firearms. Illinois belonged inside this family through the Firearm Owner’s Identification card, the state credential that placed Illinois among the states conditioning purchase on a state issued permission. The remaining states imposed no purchase permit requirement of this kind, so that across most of the country the question of advance permission never arose and the federal check at the dealer counter was the only screening a purchaser faced.

Iowa supplied the clearest demonstration, within the period covered, that the permit map was drawn by legislatures of the states and could be redrawn by them on a date certain. Iowa appeared in the Johns Hopkins count published in 2020 as one of the nine states requiring a permit to purchase at least handguns. House File 756, signed on April 2, 2021 and effective on July 1, 2021, then made the Iowa handgun purchase permit optional, leaving eight states and the District of Columbia with a mandatory purchase permit at least for handguns at the article’s August 2021 date. A handgun purchase in Iowa in June 2021 took place under a mandatory permit rule. A handgun purchase in Iowa in July 2021 took place under a rule in which the permit existed as an option rather than a condition. Nothing in federal law changed between those two transactions. The dealer license requirement, the transaction record, and the federal check were unaltered, because the layer that changed was the states’ layer, acting on a subject that section 927 left open to it. An optional permit also differed from a permit abolished, since the credential remained available to a purchaser who chose to obtain one.

Waiting periods formed the second major addition by the states to the purchase, and they operated on a different principle from permits. A permit screened the person before the transaction. A waiting period governed the interval within the transaction, interposing a delay between the purchase process and the delivery of the firearm to the buyer. A waiting period under the law of the states added time after or around the federal inquiry under section 922(t), so that completion of every federal requirement did not itself entitle the buyer to immediate possession. Waiting periods therefore regulated the tempo of a lawful purchase rather than the eligibility of the purchaser, and a buyer who passed every check and held every required permit in a waiting period state nonetheless took delivery on the state’s schedule.

The extent and the variety of waiting period law at the article’s date can be stated with the same precision as the permit map. Nine states and the District of Columbia imposed a waiting period on at least some retail purchases at the article’s date, in an enumeration published in a state by state survey by the Associated Press, and every such law predated 2021. The periods differed considerably from state to state, and the differences ran along two dimensions, the length of the wait and the class of firearms to which the wait applied. California imposed ten days for all firearms, Hawaii imposed fourteen days, and the District of Columbia imposed ten days, and those three jurisdictions sat at the long end of the range. Florida imposed three days. Illinois imposed seventy-two hours. Maryland and New Jersey applied their periods to handguns and regulated firearms. Minnesota and Washington applied their periods to handguns and semiautomatic rifles, and Washington’s period was ten business days for semiautomatic rifles under Initiative 1639 of 2018. The range, from seventy-two hours to fourteen days, tracked legislative choices about which firearms justified a delay and about how long a delay the states judged appropriate, choices that federal law neither made nor overrode.

Placed beside the permit map, the waiting period map shows how the states’ layer could combine its instruments in different proportions for the same underlying transaction. Illinois appeared in both families of law, requiring the Firearm Owner’s Identification card described in the Johns Hopkins count published in 2020 and imposing the seventy-two hour waiting period recorded in the Associated Press enumeration. Hawaii, Maryland, and New Jersey likewise appeared in both enumerations. A buyer in such a state faced a credential obtained in advance and an interval imposed at the sale, layered over the federal record and check. A buyer in a state appearing in neither enumeration faced the federal baseline alone. The practical character of buying a handgun in the United States in 2021 was therefore a set of characters of the states, each assembled from a common federal core and a selection of additions by the states.

The private transfer presented the sharpest contrast in the whole purchase field, because in a private transfer the federal baseline itself changed character. The federal check under section 922(t) attached to licensees. It was a duty of the licensed dealer, triggered by a licensee transfer, and documented on the transaction record that the licensee completed and kept. A transfer between two unlicensed persons stood outside that machinery. Federal law imposed no background check requirement on a transfer between unlicensed persons within a state, so a private sale or gift between residents of the same state, neither of whom held a federal firearms license, could proceed under federal law without a check and without any federal record of the transaction. The boundary of that federal silence was the state line. Sections 922(a)(3) and 922(a)(5) governed acquisition and transfer across state lines by nonlicensees and barred interstate private transfers outside narrow exceptions, including transfers by bequest or intestate succession and temporary loans for lawful sporting purposes. Federal law thus left the intrastate private transfer unchecked while fencing the interstate private transfer almost entirely, and the space inside the fence was a space that only the law of the states could fill.

States filled that space in divergent ways, and the divergence produced a counting problem that any honest account of the subject has to present as a pair of counts rather than a single figure. The Giffords Law Center counted twenty states and the District of Columbia requiring a background check for transfers of at least some firearms between private parties. The Center for American Progress, in a February 2021 fact sheet, counted twenty-two states and the District of Columbia. The Giffords count measured states that required a background check at the point of the private transfer itself, for at least some firearms. The Center for American Progress count rested on a broader measure, one that included permit to purchase systems reaching private sales, in which the screening of the buyer occurred through the permit process rather than through a check run at the moment of transfer. A state whose permit system reached private sales could appear in the broader count without requiring a discrete check between the parties, because the buyer arrived at the transaction already screened under the state credential. The gap of two states between the counts was therefore a gap of definition before it was a gap of fact. What differed was the question the counter had asked of the same underlying laws, and the difference records a structural feature of the subject, namely that states screened private buyers through two mechanisms, a check at the transfer and a credential held in advance.

The interaction between the private transfer rules and the permit rules shows the instruments of the states working as a system rather than as isolated requirements. In a state with a permit to purchase system reaching private sales, the permit performed for the private transaction the screening function that the federal check performed for the dealer transaction, without any dealer taking part. In a state with a point of transfer check requirement for private parties, the screening followed the buyer into the private market directly, and the parties had to reproduce, outside the licensed channel, a version of the check that federal law required only inside it. In a state with neither arrangement, the federal prohibitions on possession bound the parties as a matter of substantive law without any administrative checkpoint at which eligibility was tested before the firearm changed hands.

One further feature of the purchase completed the role of the states, concerning administration rather than substance. The federal check had to be run by someone, and the identity of the office that ran it was itself a matter of variation among the states within a federal framework. In a substantial number of states, licensees contacted the Federal Bureau of Investigation directly, and the federal system answered the inquiry. In other states, a state agency stood between the dealer and the federal system as a point of contact, receiving the dealer’s inquiry and returning the result. The fullest account of that variation for the period came from the Federal Bureau of Investigation’s NICS Operations Report for 2019, which recorded thirteen states acting as full points of contact, four states as partial points of contact for handguns, Maryland, New Hampshire, Washington, and Wisconsin, and three states as partial points of contact for handgun permit transactions, Iowa, Nebraska, and North Carolina. In a full point of contact state, the state agency handled the check for licensee transactions generally. In a partial arrangement, the state agency handled a defined slice of the traffic, handgun transactions or handgun permit transactions, and the remainder went to the Federal Bureau of Investigation directly. The variation is traced in the NICS background check law guide, and its significance for the division of labor is plain. Even the single most federal element of the purchase, the check created by section 922(t), reached the buyer in many states through the hands of the states.

Iowa’s place in the point of contact account adds a caution about dates that applies across the purchase field. The Federal Bureau of Investigation’s NICS Operations Report for 2019 placed Iowa among the three states acting as partial points of contact for handgun permit transactions, an arrangement under which the state agency’s role ran through the permit process rather than through dealer inquiries generally. That description was a description of 2019. House File 756, signed on April 2, 2021 and effective on July 1, 2021, then altered the status of the Iowa handgun purchase permit from mandatory to optional, changing the population of transactions to which any permit based arrangement could apply. An account that carried the 2019 administrative description forward without noting the 2021 statutory change would present as settled a structure that the state legislature had in part redesigned.

The point of contact arrangement had a counterpart in a second federal recognition of credentials of the states, the qualifying alternate permit. Section 922(t)(3) provided an exception to the point of sale check for a buyer who presented a state permit that federal law recognized as a substitute, a permit whose issuance under state law satisfied the federal conditions for standing in place of the check. Under that arrangement, the screening that the check would have performed at the counter had already been performed through the permit process, and the dealer completed the transfer on the strength of the credential. The Federal Bureau of Investigation’s NICS Operations Report for 2019 recorded twenty-five states having at least one qualifying alternate permit, so in twenty-five states, as counted in that 2019 report, some class of permit holder could purchase from a dealer without a fresh point of sale check. The division of labor at the point of purchase was therefore not a simple hierarchy in which the federal layer acted and the states’ layer merely added. In the alternate permit states, the states’ layer acted first, and the federal layer accepted the state act as its own requirement satisfied.

Taken together, the elements of the purchase describe a consistent allocation of authority. The federal layer licensed the commercial channel, required the transaction record and the check within that channel, defined the categories of persons barred from the market altogether, and then, through section 927, declined to occupy the field beyond those provisions. The states’ layer decided whether a buyer needed a permit obtained in advance, as the Johns Hopkins Center for Gun Policy and Research count published in 2020 and the Iowa legislation of 2021 together show. The states’ layer decided whether a buyer waited, and the Associated Press enumeration of nine states and the District of Columbia shows the range of that decision, from seventy-two hours in Illinois to fourteen days in Hawaii. The states’ layer decided whether a private transfer required a check or a credential, and the paired counts of the Giffords Law Center and the Center for American Progress in February 2021 show that decision made in forms too different for a single total. The states’ layer even supplied, in the point of contact states recorded in the Federal Bureau of Investigation’s NICS Operations Report for 2019, the channels through which the federal check ran, and supplied, in the twenty-five states with a qualifying alternate permit recorded in that report, the credential that could replace the federal check. On nearly every element beyond the licensed channel and its federal check, the governing answer was an answer of the states.

Possession, Carry, Categories and Storage: The Conduct Layer

The first two layers of the division of labor concern transactions and the records that surround them. The conduct layer concerns a different set of questions, and those questions arise after a firearm has been acquired, or in circumstances in which acquisition is not the issue at all. Who may possess a firearm at all, and who is barred from possession regardless of the route by which a firearm arrived. Whether a firearm may be carried outside the home, and under what form of authorization by the states, if any authorization is required. Which categories of firearm, and which magazines, a state permits within its borders. How a firearm must be kept when it is not in use. What happens to firearms already held when a court order places a person inside a class that federal law bars from possession. Each of those questions is governed principally by the law of the states, laid over a federal floor that is narrow in some places, categorical in others, and absent altogether in several of the areas where everyday conduct is regulated most closely. The pattern that emerges across the conduct axes is consistent. Federal law supplies a set of national prohibitions and a small number of transaction point requirements. The law of the states supplies additional prohibitions, the licensing systems that govern public carry, the category rules that govern what may be possessed, the storage duties that govern the home, and the court machinery that gives protective orders practical effect. A person subject to both layers faces the combined result, and the combined result differs from state to state because the contribution of the states differs.

The federal disqualification list forms the starting point for possession. Section 922(g) of title 18 sets out nine categories of person to whom the federal prohibition applies. The categories cover a person convicted of a felony. They cover a fugitive from justice. They cover a person who is an unlawful user of a controlled substance. They cover a person who has been adjudicated as having a mental defect or who has been committed to a mental institution. They cover certain immigration statuses specified in the statute. They cover a person dishonorably discharged from the armed forces. They cover a person who has renounced United States citizenship. They cover a person subject to a qualifying protection order, under section 922(g)(8). They cover a person convicted of a misdemeanor crime of domestic violence, under section 922(g)(9). Alongside the nine categories, section 922(n) reaches a person who is under indictment. The list is framed in terms of status and history rather than in terms of the firearm itself. A disqualification attaches to the person, and it follows that person across state lines because the source is a federal statute of general application. None of the states can remove a federal category, narrow its terms, or authorize possession by a person whom the federal list covers, and a license or permit from one of the states does not cure a federal disqualification.

The law of the states then builds on that floor in two distinct ways, and the distinction matters for understanding how the operative rule is assembled. The first way is addition. States may add categories of their own to the federal list, so that a person who falls outside all nine federal categories, and outside section 922(n), may nevertheless be barred from possession under the law of the state of residence or the state where possession occurs. The second way is enforcement through the law of the states itself. States define their own offenses and penalties for unlawful possession and carry, so a violation of a state possession rule is prosecutable as a state offense, on state terms, in addition to whatever federal exposure the same conduct creates under federal law. The result is that the operative list a person faces is the union of both layers. The federal categories apply everywhere. The categories of the states apply on top of them, and they vary, so the full list in one state is longer or shorter than the full list in another, even though the federal core is identical in both places. The floor principle explains why the layers accumulate rather than displace each other. Under section 927, chapter 44 of title 18 is not read as occupying the field to the exclusion of state law on the same subject, absent a direct and positive conflict that the two bodies of law cannot be reconciled. Possession law is the clearest illustration of that design. Congress set a national minimum list of disqualified persons. States retained authority to extend the list, and many exercises of that authority take the form of additional categories, additional offenses, and additional penalties operating in parallel with the federal scheme.

Carry presents a sharper contrast among the states, because there is no equivalent federal licensing system for ordinary public carry against which systems of the states operate as additions. At the August 2021 vantage, the law of the states sorted into three models. The first model was permitless carry, in effect in twenty states on August 1, 2021. Within that group, Vermont stood apart on the basis of long-standing practice, while the remaining states had adopted the model by statute, in a sequence that ran from Alaska in 2003 to Iowa, Tennessee and Utah in 2021. Texas had enacted its statute, House Bill 1927, on June 16, 2021, and the statute was scheduled to take effect on September 1, 2021, at which point Texas would become the twenty-first state in that group. The defining feature of the model is the absence of a license requirement under the law of the states as a condition of carry for a person otherwise entitled to possess, so the regulatory weight in such a state rests on the possession categories themselves, on place based rules enacted by the state, and on the federal floor. The second model was shall issue licensing, the large middle group among the states. Under a shall issue system, the license issues on objective criteria. The issuing authority applies stated conditions, and an applicant who meets those conditions receives the license. The third model was discretionary licensing, described as may issue, retained by a minority of states at the article’s August 2021 date, among them California, Hawaii, Maryland, Massachusetts, New Jersey and New York. Under a discretionary system, meeting threshold conditions was not the end of the inquiry. An applicant had to show a need, or satisfy a suitability judgment, administered by the issuing authority, and the authority retained a measure of judgment about whether the license should issue in the individual case. The difference between the second and third models is therefore not a difference in whether a license exists. Both models use a license. The difference lies in what the license decision turns on, objective criteria in the one case and an evaluative judgment about need or suitability in the other. At the article’s date, the constitutional validity of discretionary licensing was contested in litigation that remained unresolved, and that contest is recorded here as a fact about the state of the law in August 2021. The doctrinal development of that question belongs to the treatment of firearms litigation elsewhere in the series, and no later doctrine is imported into an account fixed at the August 2021 vantage. For the comparison at hand, the significant point is structural. Two states could share the same federal possession floor, the same federal transaction rules, and the same absence of a federal carry license, and yet present entirely different legal environments for carry, because one had removed the license requirement, one issued the license on objective criteria, and one conditioned the license on an official judgment about the applicant.

Categories of firearm illustrate the reverse configuration, a field in which a federal rule once existed and had ceased to operate by the vantage, leaving rules of the states as the operative category law. At the August 2021 date, no federal category ban was in force. The federal statute enacted in 1994 had expired by its own terms in 2004, and the history and operation of that statute belong to a separate treatment. The states’ layer, by contrast, contained category and magazine restrictions in a minority of states, and the counts require care because two documented compilations, drawn in different years and framing the question in different terms, produced different figures. A compilation published in June 2020 recorded nine states and the District of Columbia restricting magazines above a capacity limit. The nine states in that June 2020 compilation were California, Colorado, Connecticut, Hawaii, Maryland, Massachusetts, New Jersey, New York and Vermont. The limit in Colorado stood at fifteen rounds, and the limits in the group generally stood at ten rounds. The same June 2020 compilation recorded that seven of those states also restricted specified semiautomatic firearms. Those seven were California, Connecticut, Hawaii, Maryland, Massachusetts, New Jersey and New York, with the Hawaii restriction reaching assault pistols, and the District of Columbia also restricted specified semiautomatic firearms. A separate survey published in Law and Contemporary Problems in 2020 counted the position in 2019 and arrived at a narrower figure, six states plus the District of Columbia banning assault weapons generally, with the prohibition in Hawaii reaching assault pistols. The two figures are not in conflict once the sources and dates are kept attached to them, because the June 2020 compilation counted states restricting specified firearms within a magazine restriction group, while the 2020 survey counted states with a general ban in 2019, and different framing produces different totals. That is why every count in this area carries its source and its date in the sentence that reports it. A further feature compounds the variation. Definitions of the states differed from the expired federal definition, and definitions of the states differed from each other. Two states could both be counted as restricting a category of semiautomatic firearm, and yet restrict different firearms, because the statutory definitions doing the work in the two states were written differently. Magazine rules show the same pattern in miniature, since the numerical limit is only one element, and Colorado’s fifteen round limit within a group generally set at ten rounds demonstrates that even a shared form of restriction, a capacity ceiling, was set at different levels in different states. Category law at the August 2021 vantage was therefore the law of the states in substance as well as in form, with no operative federal category rule behind it, and with internal variation driven by definitions as much as by the decision to restrict at all.

Storage law carries the pattern further, because the federal contribution in this area is confined to a single requirement imposed at the point of sale, while any general duty governing how firearms are kept in the home comes from the law of the states or does not exist at all. Federal law imposed no general home storage mandate. The federal provision is section 922(z), added by the Child Safety Lock Act of 2005, enacted as Title II of Public Law 109-92. Section 922(z) requires a licensee to provide a secure gun storage or safety device with each handgun sale, delivery or transfer, subject to statutory exceptions. The requirement is attached to the transaction and to the licensee. It governs what must accompany a handgun when a licensee transfers it. It does not prescribe how a purchaser must store a firearm in the home afterwards, what container must be used, or what duty applies when a firearm is not in use. Storage duties of that general kind were the law of the states where they existed. Massachusetts occupied a singular position in that state landscape. According to the Giffords Law Center, Massachusetts was the only state whose law required every firearm, when not in use or under the owner’s control, to be secured in a locked container or fitted with a tamper resistant locking device. It applied to every firearm, it applied whenever the firearm was not in use or under the owner’s control, and it specified the means, a locked container or a tamper resistant locking device. No other state had a universal locking requirement of that form at the vantage. Around that single universal rule sat a larger and more varied body of law addressed to child access. A tally compiled by the Giffords Law Center and reported in 2019 counted twenty seven states and the District of Columbia with child access prevention laws in 2019. Those laws varied markedly in strength. At one end of the range, liability attached only where a child actually gained access to a firearm. At the other end of the range, liability attached where access was merely likely. Between those poles, states set different triggers, different age boundaries and different consequences, and the shared label describes a family of laws rather than a single model. Several other states penalized access after the fact, or imposed no such penalty at all. The storage axis therefore divides into three distinct legal objects that are easily confused when described without their sources. A federal device requirement operates at the moment of a licensed handgun transfer. A single state imposed a universal locking duty governing firearms not in use or under the owner’s control. A group of twenty seven states and the District of Columbia, counted in a Giffords compiled tally reported in 2019, imposed child access prevention laws of varying strength. A state could appear in the third group without having anything resembling the Massachusetts rule, and a licensed sale in any state carried the federal device requirement regardless of whether the state had enacted a storage duty of its own.

Protective orders bring the conduct layer full circle, back to the federal possession categories, and the seam between the federal prohibition and the machinery of the states is the central feature of this axis. Sections 922(g)(8) and 922(g)(9) supply federal prohibitions. The first covers a person subject to a qualifying protection order. The second covers a person convicted of a misdemeanor crime of domestic violence. Federal law thereby defines who may not possess. Federal law, however, enacted no procedure requiring a prohibited person to surrender firearms already held. The Giffords Law Center’s account of the federal scheme states the point directly, and the federal statute does not address surrender. The gap is structural rather than incidental. A prohibition answers the question of legal status. A surrender procedure answers a different question, what physical steps follow, who orders the transfer of firearms already in a person’s possession, to whom firearms are delivered, what proof of compliance is required, and by what process firearms may later be retrieved if the legal position changes. Congress enacted the status rule without the accompanying machinery, so the machinery, where it exists, is machinery of the states. States divide on whether to supply it. Some states authorize or direct courts to order surrender, and set proof and retrieval procedures around the order. California is a documented example of a state with surrender machinery of that kind. Washington is another documented example, and the Washington statute, RCW 9.41.800, directs surrender orders. Other states rely on the prohibition alone, leaving the federal possession bans and the possession bans of the states to operate without a procedure of the states that collects firearms from a person who has come under the prohibition. The practical difference between the two groups is considerable, even though the underlying prohibition may be worded in similar terms. In a state with surrender machinery, a court order sets a process in motion, with defined steps and defined proof. In a state without such machinery, the prohibition states a legal duty and attaches consequences to its breach, but no dedicated process stands between the order that creates the status and the firearms the person already holds. A related instrument of the states developed alongside surrender law and performs a distinct function. Extreme risk protection order laws create a civil order aimed at temporary removal of firearms from a person found to present a risk, and the order operates on its own terms rather than as a consequence of a criminal conviction or a protection order between parties. Everytown’s count for 2021 placed extreme risk protection order laws in nineteen states and the District of Columbia by 2021. The nineteen states in Everytown’s 2021 count were California, Colorado, Connecticut, Delaware, Florida, Hawaii, Illinois, Indiana, Maryland, Massachusetts, Nevada, New Jersey, New Mexico, New York, Oregon, Rhode Island, Vermont, Virginia and Washington. The list is significant for the comparison in two respects. It includes states that appear elsewhere in the conduct layer as states with purchase licensing, category restrictions or storage duties, and it also includes states that do not share that profile, which reflects the fact that the extreme risk instrument was adopted on a separate track from the other conduct rules and does not track any single state model across the other axes. The protective order axis thus completes the argument of the conduct layer. The federal layer defines disqualified status, in the protection order category and in the domestic violence misdemeanor category, with national uniformity. Everything that turns status into a physical process, surrender orders, proof, retrieval, and temporary removal under a civil order, was built by states, was built in only some states, and differed in design among the states that built it.

Taken together, the five conduct axes describe a single allocation of work repeated in different forms. Possession begins with a federal list and grows by addition by the states, so the operative list is a union. Carry has no federal licensing counterpart for ordinary holders and sorts into three models of the states that differ in whether a license exists and in what the license decision turns on. Categories rest on restrictions of the states counted by named sources in June 2020 and in a 2020 survey of the position in 2019, on definitions of the states that differ from the expired federal definition and from each other, with no federal category ban in force at the August 2021 vantage. Storage rests on a federal device requirement at licensed handgun sale, a universal locking rule in one state, Massachusetts, and child access prevention laws in twenty seven states and the District of Columbia in the Giffords compiled tally reported in 2019. Protective orders rest on federal prohibitions without a federal surrender procedure, on surrender machinery in some states and reliance on the prohibition alone in others, and on extreme risk protection order laws in nineteen states and the District of Columbia in Everytown’s count for 2021. In each case the layer that a national debate tends to describe, the federal layer, supplies either a floor or a status rule or a transaction point requirement, and the layer that determines the content of daily conduct, the states’ layer, supplies the additions, the licenses, the definitions, the storage duties and the court procedures. That allocation is the conduct layer’s contribution to the comparison, and it holds across axes that otherwise have little in common beyond the fact that both levels of government legislated, or chose not to legislate, within the space that the floor principle left open.

The Commandeering Bar: Neither Government Conscripts the Other

The division between federal and state firearms law rests on more than a division of subjects. The division also rests on a division of personnel. Congress may enact a federal rule, and a state legislature may enact a state rule, and a person subject to both layers must reckon with both. A separate question asks who must administer a rule once enacted. The anti-commandeering doctrine answers that question by placing a limit on the means available to Congress. The federal government may not conscript a state legislature into enacting a federal program, and the federal government may not conscript state executive officers into carrying a federal program out. The limit does not erase a federal statute, and the limit does not free anyone from a valid federal rule governing private conduct. The limit addresses the machinery of government itself.

That distinction separates commandeering from preemption. Preemption concerns the relationship between two rules of conduct, where a state rule and a federal rule point in different directions for the same act. Commandeering concerns the relationship between two governments, where one government attempts to direct the lawmaking or law enforcement apparatus of the other. A dispute over preemption therefore asks which rule governs conduct, while a dispute over commandeering asks whether Congress used a permissible method at all. The firearms field presents both kinds of question, because the federal statutes license a commercial channel, define categories of persons barred from possession, and rely in part on a background check system with a federal component and, in a number of states, a state component.

Why did the Brady Act’s interim system run through state officers at all?

Because the Brady Act created an interim arrangement to operate before the forthcoming federal check system took its place. During that interval, federal law directed chief law enforcement officers to make a reasonable effort to conduct background checks on prospective handgun purchasers, using state and local officers rather than a completed federal apparatus.

The interim design had a practical logic that the constitutional objection later displaced. State and local officers were distributed across the country, held working relationships with local records, and stood closer than any new federal office to the communities where handgun sales occurred. A federal statute that borrowed that existing network could begin operating without waiting for a federal system to be built and staffed. The borrowed network, however, was not a federal network. The officers in question held state and local offices, drew authority from state and local law, and answered through chains of command that Congress had not created. The interim provisions did not merely invite cooperation. As described in the Brady Act guide, the provisions placed a duty on chief law enforcement officers as a matter of federal command, and that feature formed the ground on which the arrangement was challenged and, in a defined and limited respect, struck down.

Printz v. United States, 521 U.S. 898 (1997), supplied the governing statement of the doctrine in the firearms setting. The Supreme Court decided Printz on June 27, 1997, by a vote of five to four. The holding was drawn with unusual narrowness, and precision about the holding matters more than any broader slogan drawn from the case. Printz did not invalidate the Brady Act as a whole. Printz did not hold that background checks were beyond federal power, and Printz did not hold that a state could bar the federal government from operating a federal check system of its own. The decision addressed a particular method, the conscription of state executive officers, and the relief granted corresponded to that method and to nothing wider.

The exact scope of the invalidation deserves statement in precise terms. Printz invalidated only the interim Brady provision commanding chief law enforcement officers to make a reasonable effort to conduct background checks, the command set out at section 922(s)(2) of title 18. Printz also invalidated the implied duty to accept completed Brady forms under section 922(s)(1)(A)(i)(III) and (IV). Every other element of the structure survived the decision. The waiting period survived. The duties imposed on federal firearms licensees survived. State alternative systems survived. The forthcoming federal system survived as well, so the path toward a federally operated check remained open after the interim command fell. A reading that treats Printz as a judgment against background checks in general therefore misstates the case. The case removed a commanded role for state officers and left the surrounding federal scheme, including a federal check performed by federal means, intact.

The reasoning behind that limited result reaches the character of state office itself. A chief law enforcement officer holds an office created by state law, and the responsibilities of the office are ordinarily assigned through state law and state political processes. A federal command that adds a federal duty to that office redirects the officer’s time and the accountability that runs between the officer and the community the office serves. Residents dissatisfied with a federally commanded task would have no clear government to hold responsible, since the government that issued the direction did not appoint, fund, or remove the officer. The doctrine treats that diffusion of accountability as a structural defect rather than a mere inconvenience.

Printz did not arise without a lineage, and the earlier decision in the line explains why the Brady command presented a problem even though the command ran to executive officers rather than to a legislature. In New York v. United States, 505 U.S. 144 (1992), the Supreme Court held that Congress may not compel a state legislature to enact a federal program. The principle in New York concerned legislation, the most distinctly sovereign act a state performs, and the decision denied Congress the power to turn a state legislature into an instrument for adopting a federal scheme. The reasoning did not depend on agreement or disagreement with the substance of the program in question. A state legislature that enacts a law under federal compulsion produces a statute whose political authorship is misleading, because the legislators who voted for the measure acted under a federal order rather than under a judgment for which state voters could hold those legislators to account. New York therefore established the legislative side of the bar before Printz addressed the executive side.

Read together, New York and Printz cover the two principal ways a state government acts, through legislation and through execution. A doctrine that barred only legislative conscription would have left executive conscription available as a substitute route to the same result. Printz closed that route. The relative modesty of the assigned task made no saving difference, because the defect lay in the command itself rather than in the weight of the burden the command imposed.

The third decision in the lineage extended the same principle to a federal order framed in negative terms. In Murphy v. National Collegiate Athletic Association, 584 U.S. 453 (2018), the Supreme Court held that Congress may not issue direct orders to state legislatures, including an order to maintain a prohibition. The formulation matters because a prohibition on repeal might appear to involve no affirmative lawmaking at all. A legislature ordered to keep an existing prohibition in place has not been told to draft a new statute, yet the legislature has been denied control over a subject within its legislative competence, and the content of state law on that subject has been dictated by Congress. Murphy treated that denial as a direct order. The line from New York through Printz to Murphy thus runs in both directions, against a command to enact and against a command to refrain from repealing.

The three decisions also mark the boundary between the doctrine and ordinary federal supremacy. A valid federal statute governing private conduct displaces a conflicting state statute, and nothing in the commandeering cases withdraws that consequence. The doctrine operates at an earlier point, on the choice of instrument. Congress may regulate private conduct and may administer a federal program through federal personnel. Congress may not draft a state legislature or state officers into service as the means of regulation.

In practice, the doctrine produces a background check system built on federal administration and voluntary state participation rather than on command. The federal check is run by federal staff, or the check is run by a state agency that has taken on the role of a point of contact between licensees and the federal system. A point of contact state receives the inquiries generated by sales within the state, searches available records, and communicates the result through the federal process. A state that serves in that role does so as a participant in an arrangement the state has accepted, and the arrangement differs in kind from the interim Brady command for exactly that reason. Participation rests on a state decision and can be structured through the state’s own agency and procedures. The federal system, for its part, must be capable of operating where no state participates, because the federal obligation to run the check cannot depend on personnel the federal government has no power to conscript.

The participation pattern recorded in the FBI’s NICS Operations Report for 2019 shows how varied the resulting arrangements became. Per that report, thirteen states acted as full points of contact, handling the check function for licensees within their borders. Four states, Maryland, New Hampshire, Washington, and Wisconsin, were partial points of contact for handguns. Three states, Iowa, Nebraska, and North Carolina, were partial points of contact for handgun permit transactions. In the remaining states, licensees contacted the FBI directly, and federal staff performed the check. The same federal report recorded that twenty-five states had at least one ATF qualified alternate permit, a state issued permit that could stand in place of a check at the point of sale where the permit met federal standards. Each arrangement reflects a state choice operating alongside a federal system, and the patchwork quality of the map is itself a consequence of the doctrine. A commanded system would have produced uniformity of administration. A voluntary system produces variation in administration beneath a federal rule that applies everywhere.

Variation of that kind carries consequences the doctrine accepts rather than resolves. Agencies of the states may bring local knowledge to the task, but agencies of the states also consume resources of the states on a function that federal law requires, and the allocation of those resources involves the kind of priority judgment that the commandeering bar reserves to the states.

The power of a state to withdraw cooperation follows from the same allocation. A state that serves as a point of contact may end that service, and a state that declines the role from the outset acts within the doctrine in doing so. Withdrawal does not repeal the federal check and does not excuse a licensee from obtaining a check before a transfer. Withdrawal changes only the identity of the personnel who perform the federal function. After a withdrawal, the check falls to federal staff, and the burden of administering federal law returns to the government that enacted the law. That consequence expresses the doctrine’s central bargain, under which Congress gains the power to legislate and to administer federal legislation through federal means, while a state retains control over state officers whose offices the state created.

Federal enforcement more broadly follows the pattern the background check illustrates. Federal enforcement runs through federal officers and federal courts, and a federal firearms offense proceeds through that federal machinery. At the same time, most street level enforcement of both layers is carried out by officers of states and localities acting under the law of the states. A patrol officer who encounters a firearm during a stop applies state law on possession and carry, and any federal dimension ordinarily arrives through a referral to federal authorities rather than through the officer acting as a federal agent. The commandeering bar preserves exactly that separation, ensuring that the volume of enforcement activity by the states never converts, by inference, into a federal entitlement to direct effort by the states.

The doctrine has limits that are as important to its meaning as the bar itself. A state may decline to lend state officers to the enforcement of federal law, but a state may not obstruct federal officers in the performance of federal duties. Noncooperation consists of a refusal to assist, a decision to direct state resources elsewhere, or a withdrawal from a voluntary arrangement. Obstruction consists of affirmative interference with federal action. The first category falls within the protection the doctrine affords to state autonomy. The second category falls outside that protection, because a state that obstructs federal enforcement does not merely withhold state assistance but instead impedes the federal government in the use of federal means. Nullification stands on the far side of the same line. A state may repeal a state prohibition or decline to enact a state offense parallel to a federal offense, but a state may not declare a valid federal statute void within state borders or excuse residents from compliance with federal law. A difference in enforcement intensity between a cooperating state and a noncooperating state is therefore not a difference in legal obligation. Federal prohibitions, federal licensing duties, and federal transfer rules bind in every state regardless of the posture a state adopts toward assistance.

The symmetry of the doctrine deserves emphasis, because the firearms setting can make the principle appear to belong to one side of a policy debate. The bar protects a decision of the states to withhold officers from federal firearms administration, and the bar protects a decision of the states to withhold officers from federal enforcement in other fields as well, on identical reasoning. The doctrine does not inquire whether Congress or a state legislature holds the better view of the underlying subject. The doctrine inquires only whether Congress attempted to govern through machinery of the states rather than through federal machinery or through direct regulation of private conduct. A state whose officials support a federal program may cooperate extensively, and a state whose officials oppose a federal program may cooperate hardly at all, and the doctrine accommodates both postures because the choice belongs to the state in either case.

The federal drug field supplies the worked example of the doctrine operating outside firearms, and the example is treated here briefly and by reference rather than by reargument. States repealed marijuana prohibitions of the states while the federal prohibition remained in force, and the repeal of a state prohibition required no federal permission, because a state legislature cannot be commanded to maintain a prohibition on state law books. Federal enforcement of the federal prohibition remained a federal task, carried out by federal officers through federal courts, and residents remained subject to the federal prohibition regardless of the change in the law of the states. The parallel with firearms administration holds at the level of structure, where a state decision about state law and state personnel left a federal rule intact and a federal responsibility undiminished. A fuller treatment of the substance and the enforcement history appears in the federal drug law and state law comparison, and the structural point stands without that substance. A state controls state law and state officers, and the federal government controls federal law and federal officers, and neither government governs by conscripting the other.

The commandeering bar therefore shapes firearms law less by changing any rule of conduct than by determining the institutional form that federal rules take. Because Congress could not command chief law enforcement officers to run interim checks, the federal check developed as a federal system, supplemented in a substantial number of states by agencies that volunteered for a point of contact role. Because Congress cannot command a state legislature, policy on firearms in the states exists as genuine policy of the states, adopted and repealable through processes of the states, rather than as a federal script performed by actors of the states. Because a state cannot obstruct or nullify, the federal layer operates everywhere, and a decision of the states to stand aside changes enforcement arrangements rather than legal duties. Friction between the layers appears most often not over what the law says, but over whose officers, whose budgets, and whose priorities carry the law into effect.

Local Preemption: The State’s Treatment of Its Cities

The comparison between federal law and the law of the states describes only the first level of division in American firearms regulation. A second level operates inside each state, between the state government and the governments of its cities, counties, and other local units. That second level is governed, in large part, by preemption. Preemption in this setting means a rule of the higher government displacing a rule of the lower government on the same subject. A state statute preempts a local ordinance when the statute takes the subject away from local decision, either by declaring that result in words or by occupying the subject so completely that a local rule on the same matter cannot stand alongside the state rule. The practical question for a resident therefore requires more than identifying the state rule. The practical question also requires asking whether a city was permitted to add a rule of its own, and whether a city that attempted such a rule faced consequences beyond the loss of the ordinance itself. Those questions turn on the law of the state in which the city sits, and the answers differed sharply from state to state at the article date of August 1, 2021.

The subject is a second-order federalism question because the structure repeats at a smaller scale. At the first level, federal law and the law of the states bind at the same time, and a state may forbid or condition conduct that federal law merely permits unless a direct and positive conflict prevents the two layers from standing together. At the second level, state law and local law bind at the same time, and the distribution of authority between a statehouse and a city hall decides whether local variation exists at all. The operative comparison for a resident is therefore not only Washington against the states. The operative comparison is also the statehouse against city hall. A state may have comparatively few statewide rules on a subject, yet a city in that state may have no power to supply a missing rule if a preemption statute has reserved the whole subject to the state. Silence by the states and local authority are separate matters, and permission by the states and local permission are also separate matters. Preemption doctrine is the mechanism that separates them.

Express preemption and implied preemption accomplish that separation through different routes. Express preemption begins with language. A legislature enacts a statute that states, in substance, that local governments may not regulate a defined subject, or that regulation of that subject is reserved to the state, or that local ordinances on that subject are void. The displacement follows from the words the legislature chose, and a court asked to decide the fate of a local ordinance begins with that text. Implied preemption reaches a similar result without a declaration in those terms. A court may conclude that a comprehensive state scheme leaves no room for a local rule on the same subject, or that a particular local rule conflicts with a state rule by forbidding what the state rule permits or by permitting what the state rule forbids.

The breadth of the reserved subject gives express preemption its force. A statute may preempt a narrow topic, leaving local governments free to regulate other aspects of firearms activity, or a statute may preempt a field described in general terms, leaving little room for local rules of any kind within that field. The Giffords Law Center taxonomy described in this section sorts states by the presence and scope of express statutes on local firearms regulation, and the most common category in that taxonomy was the broad one. According to that taxonomy, the remaining forty-three states expressly preempted all or substantially all local firearms and ammunition regulation. A formulation of that kind answers many local questions at once. A city council in such a state considering an ordinance on purchase, possession, carry, storage, sale, or ammunition would first have to find authority outside the preempted field, and for subjects inside the field no such local authority existed. The ordinance would fail not because the state legislature rejected its policy in a vote on that ordinance, but because the legislature had decided in advance, through the preemption statute, that the subject belonged to the state alone.

Can a city prohibit what its state permits?

In a state with an express preemption statute covering the subject, a city generally may not prohibit what its state permits, because the state statute displaces the local ordinance. In the five states without an express statute identified by the Giffords Law Center, a city has more room, although conflict and implied preemption doctrines confine that room.

The history of the modern statutes explains why so many legislatures of the states addressed the subject during a relatively concentrated period. The preemption wave followed the Village of Morton Grove, Illinois handgun possession ban of 1981, upheld by the Seventh Circuit in 1982 in Quilici v. Village of Morton Grove. Morton Grove was a municipality, and its ban demonstrated, in a concrete and litigated form, that a local government exercising local authority could adopt a prohibition on handgun possession that went beyond the rules of its state. The Seventh Circuit decision in Quilici left that ban in place, and the episode acquired significance far beyond one village. For supporters of statewide uniformity, the episode showed that a patchwork could arise one municipality at a time, with a resident crossing a municipal boundary into a different set of possession rules. The legislative response recorded in that history was the wave of state preemption statutes that followed, and most state preemption statutes dated from the mid-1980s onward. The timing matters to the taxonomy. The categories described for 2021 were largely the product of statutes enacted in a defined period, in reaction to a defined event, and the categories remained open to legislative change, as a repeal enacted in Colorado in June 2021 demonstrated.

The Giffords Law Center taxonomy of express preemption statutes stated the national distribution in three categories, and each category deserves separate attention because the legal position of a city differed in each. Five states had no express statute preempting local firearms regulation, according to that taxonomy. The five states were Connecticut, Hawaii, Massachusetts, New Jersey, and New York. Two states had limited express preemption, according to that taxonomy. The two states were California and Colorado. The remaining forty-three states had express statutes preempting all or substantially all local regulation, according to that taxonomy. The three figures account for every state, sorting each state by the form of its express law rather than by the content of its statewide firearms rules. A state could appear in any of the three categories whatever its statewide rules on purchase, carry, or storage provided. The taxonomy measured who decided, not what was decided. That measurement is the reason the taxonomy belongs in a comparison of federal and state law. A comparison that reports only the content of statewide rules misses the allocation of authority that determines whether content may vary within a state.

The category of no express preemption requires careful reading, because the absence of an express statute did not mean the absence of limits on local law. In Connecticut, Hawaii, Massachusetts, New Jersey, and New York, the five states named in that category by the Giffords Law Center, a city began the inquiry without a statute that expressly reserved the subject of firearms regulation to the state. A city in one of those states could look to its general municipal authority, to any state statute granting or limiting authority on a particular subject, and to the body of state law against which a proposed ordinance would operate. That starting point gave local governments more room than local governments possessed in a state with a broad express statute. The room was confined, however, by doctrines that operate without an express reservation. Conflict preemption displaced a local rule that contradicted a state rule, and implied preemption displaced a local rule on a subject that state law occupied in a manner that left no space for local supplementation. A local ordinance in one of the five states therefore had to survive two kinds of examination. The ordinance had to rest on local authority, and the ordinance had to coexist with state law.

The limited category occupied a middle position, and the two states named in that category by the Giffords Law Center, California and Colorado, illustrate why the middle position requires reading the particular statute rather than relying on the category label alone. Limited express preemption means that a statute expressly preempted some local regulation and left other local regulation outside the reservation. The line between the reserved part and the unreserved part becomes the decisive line for a city in such a state. An ordinance on the reserved side of the line falls under the express statute. An ordinance on the other side of the line faces the ordinary conflict and implied preemption inquiries, and a city defending such an ordinance argues from the limits the legislature itself placed on the reservation. The category also shows that preemption is a matter of degree in statutory design. A legislature may reserve the whole field, reserve part of the field, reserve a named subject, or enact no express reservation at all. Each choice distributes authority differently between the statehouse and city hall, and each choice leaves a different body of local law standing.

Colorado supplied the clearest illustration of movement within the taxonomy at the article date. The legislature of Colorado in June 2021 repealed most of its preemption statute, the first such repeal in the nation, restoring broad local authority. That event carries several lessons for reading the taxonomy as a whole. First, the categories were legislative choices, subject to revision by the same institution that created the categories, and a state counted in one category in one year could occupy a different position after a repeal or an enactment. Second, the restoration of broad local authority did not by itself enact any local rule. The repeal returned decision making power to local governments, and any particular ordinance depended on a local government exercising that returned power and on the ordinance surviving the conflict and implied preemption doctrines that operate in every state. The Colorado repeal therefore changed who could decide across a broad range of local firearms questions in Colorado, without dictating the content of any resulting local decision.

The forty-three state category, as the Giffords Law Center taxonomy described that category, represented the dominant national pattern at the article date. In those states, an express statute preempted all or substantially all local firearms and ammunition regulation. The phrase all or substantially all does important work in that description. A statute in that category did not merely resolve a conflict between one ordinance and one state rule. A statute in that category withdrew a subject, or nearly the whole subject, from local government competence. A resident of a city in one of those states who read a local ordinance that appeared to impose a firearms requirement beyond state law would therefore ask a threshold question before reaching the ordinance content. The threshold question was whether the ordinance survived the state preemption statute at all. In many instances that threshold question disposed of the matter. The ordinance was void, or a court would treat the ordinance as unenforceable, because the state had reserved the subject. The practical consequence followed directly: residents seeking a change in firearms rules in such a state addressed the state legislature, because the city council lacked power to deliver the change.

A further dimension, documented separately from the basic taxonomy, added penalties aimed at local officials themselves. Research led by Jennifer Pomeranz of New York University, reported in May 2021, counted states with punitive preemption provisions rising from two in 2009 to fifteen in 2018. Punitive preemption in that research meant provisions that attached penalties to the act of enacting or enforcing a preempted local rule, directed at the local government or at the officials responsible. The increase from two states in 2009 to fifteen states in 2018, in the Pomeranz research reported in May 2021, shows that the development of preemption law between those years involved more than the spread of express reservations. The development also involved a change in the consequences of testing a reservation. An ordinary preemption statute risked the ordinance. A punitive provision risked a sanction for the officials who adopted or enforced the ordinance, and that difference alters the behavior of a city government considering a rule at the boundary of a reserved subject.

Florida and Kentucky supplied the documented examples of the two forms such a sanction took in the material available at the article date. The statute of Florida fined officials up to 5,000 dollars. The law of Kentucky imposed criminal penalties. A fine of up to 5,000 dollars, in the Florida example, is a personal financial consequence attached to official action, distinct from a judgment that an ordinance is void. Criminal penalties, in the Kentucky example, place official action within the framework of criminal liability, a consequence of a different order from invalidation of the ordinance itself. The two examples should not be merged into a general description of every punitive provision counted in the Pomeranz research reported in May 2021. The research counted fifteen states with punitive preemption provisions in 2018, and the forms of penalty varied by state. The Florida and Kentucky examples establish the range that such provisions reached, from a substantial fine to criminal exposure, and that range explains why the punitive dimension receives separate treatment in an account of local authority.

The practical consequences of the whole structure fall into a small number of recurring patterns. In states with broad express statutes, city ordinances within the reserved field were voided, or were never enacted because the reservation made the outcome of an attempt predictable. In states with punitive provisions, the deterrent reached earlier in the process, at the point of drafting and voting, because officials faced penalties in addition to invalidation. In states with limited express preemption, consequences followed the statutory line, with ordinances on the reserved side displaced and ordinances on the other side tested under general doctrine. In one of the five states with no express statute, named in the Giffords Law Center taxonomy as Connecticut, Hawaii, Massachusetts, New Jersey, and New York, a city ordinance had a wider field in which to operate, and even there conflict and implied preemption doctrines confined local law, so that an ordinance contradicting state law or entering a subject state law occupied could fall without any express statute commanding that result. Across all four patterns, the decisive legal work was done by the law of the states. Federal law supplied no general rule allocating authority between a state and its cities on firearms regulation, and the federal floor principle that permits a state to add to federal law says nothing about whether a state permits its cities to add to state law.

That point connects local preemption to the deciding factor of the comparison as a whole. The practical rules for a reader are set by the state of residence and by that state’s treatment of its cities. In a preempting state, the rules for a resident on firearms were set entirely at the state capital for the subjects the statute reserved, because no city, county, or other local unit could maintain a different rule on those subjects. In a state without a broad reservation, by contrast, a move across a municipal line could place a resident under a different local rule on a subject that local authority reached, provided the rule survived conflict and implied preemption examination. The difference between those two experiences of residence within a single state is the human content of preemption doctrine. The doctrine reads as an abstract rule about the hierarchy of laws. The doctrine operates as a decision about which government a resident must persuade, which government made the rule in force on a particular street, and which level of government bears responsibility for that rule.

Movement Across State Lines and the Carry Patchwork

A line between states changes the legal setting around a firearm even when the firearm, its owner, and the purpose of a journey remain the same along the route. Federal law speaks most directly to acquisition, transfer, and transport, the acts by which a firearm changes hands or moves between places. The law of the states speaks most directly to possession and carry at the destination, the holding or bearing of a firearm once the journey ends. A single crossing can therefore present several distinct questions in sequence: whether a firearm may be acquired outside the state of residence, whether one private person may transfer a firearm to a resident of another state, what channel federal law provides when a licensee stands on one side of the line and a buyer on the other, whether a firearm may be transported through intervening states between two places of lawful possession, and whether a permit to carry issued by one state has any effect in another state. Federal law answers the acquisition, transfer, and transport questions through the Gun Control Act. Federal law answers the carry question for only one defined class of persons, and for everyone else the answer sits in the law of each state entered. Keeping those questions separate is the central discipline of the interstate subject, because a provision authorizing one act does not authorize the others.

The starting point is the federal treatment of acquisition by a person who holds no federal firearms license. Section 922(a)(3) of title 18 bars a non-licensee from acquiring a firearm outside the state of residence, subject to narrow exceptions stated in the statute. A purchase that would proceed through ordinary channels inside the state of residence becomes a federal problem when the same person acquires the firearm across a state line, because the statute reserves interstate acquisition to the channels the Act itself describes. The buyer’s home state is the jurisdiction whose purchase rules the federal scheme treats as the baseline for that buyer, and section 922(a)(3) holds the individual acquirer to that baseline, before any question about dealers or shipment arises. Its exceptions are narrow and specific rather than general. The statutory scheme records bequests and intestate succession among them, the routes by which a firearm passes from a deceased owner through an estate, together with temporary sporting loans, in which possession passes for a limited sporting purpose without the permanent change of ownership that an acquisition involves. None of those exceptions creates a general interstate market for private acquisition, and none turns presence in another state into a basis for buying there. Each addresses a defined circumstance in which possession crosses a state line without an ordinary purchase, and each leaves the general bar intact for the ordinary case.

The companion provision governs the other side of a private transaction. Section 922(a)(5) bars a non-licensee from transferring a firearm to a person who resides in another state, again subject to narrow statutory exceptions. Where section 922(a)(3) speaks to the person acquiring, section 922(a)(5) speaks to the person giving, selling, or otherwise transferring, and the pairing closes both ends of a transaction that either participant might regard as a purely private arrangement. Federal law treats the arrangement differently. A transfer between residents of different states crosses the boundary that the Gun Control Act uses to organize the commercial channel, and the Act responds by barring the direct private route and directing interstate changes of ownership toward licensed intermediaries. The same narrow exceptions appear in this setting, including bequests and intestate succession and temporary sporting loans. A bequest is not a market transaction arranged between living parties, and a temporary loan is not a transfer of ownership at all, so neither exception undermines the structure of the bar. Outside those defined circumstances, a private transferor in one state and a private transferee in another do not complete a lawful interstate transfer by agreement between themselves. The statute asks where each party resides, and on that fact the direct private channel closes.

The licensed channel operates under a different provision, because Congress placed the commercial trade in firearms in the hands of federal licensees and then regulated how licensees deal across state lines. Section 922(b)(3) governs sales by a licensee to a buyer who resides in another state, and it draws a sharp distinction between long guns and handguns. A long gun may be sold face to face by a licensee to an out-of-state buyer only when the transaction satisfies the laws of both states, the state where the licensee does business and the state where the buyer resides. Federal law permits the sale to occur outside the buyer’s home state, and in the same provision federal law refuses to let that permission displace either state’s law. The licensee’s state contributes its conditions for the sale, and the buyer’s state contributes its conditions for a resident acquiring that firearm. Both sets of conditions apply at once, and a sale that satisfies one set while failing the other does not satisfy section 922(b)(3). The face to face character of the transaction forms part of the provision’s design. The buyer appears in person before the licensee, the licensee conducts the transfer as a licensee transfer, with the transaction record and the background check that accompany licensee transfers under federal law, and the firearm passes directly from the licensee to the buyer. The provision therefore creates a genuine interstate retail route for long guns, fenced on both sides by state law and completed through a licensee rather than through any private arrangement.

Handguns follow a narrower route under the same subsection, and the difference between the two routes reveals how the federal scheme weighs residence. A licensee may not hand a handgun directly to a buyer who resides in another state at all. A handgun reaches an out-of-state buyer only through a licensee in the buyer’s own state of residence. The mechanism operates by shipment between licensees: the selling licensee sends the handgun to a licensee in the buyer’s home state, and the transfer to the buyer occurs there, conducted by that licensee in the buyer’s state of residence. The buyer’s home state law therefore governs the completed transfer in the ordinary way, because the transaction that places the handgun in the buyer’s hands happens inside that state and through that state’s licensed channel. For a long gun, section 922(b)(3) accepts an out-of-state completion and compensates by requiring compliance with both states’ laws. For a handgun, the subsection declines the out-of-state completion entirely and relocates the transfer to the buyer’s state. In neither case does the licensee channel erase the state line, and the buyer’s residence remains legally significant at every step of an interstate purchase from a dealer.

Movement of a firearm already owned presents a separate question from acquisition or transfer, and federal law answers that question in section 926A, the interstate transport provision enacted as part of the Firearms Owners’ Protection Act of 1986. Section 926A provides that a person not otherwise prohibited by law from transporting, shipping, or receiving a firearm may transport a firearm for a lawful purpose from a place where that person may lawfully possess and carry the firearm to another place where possession and carry are likewise lawful, notwithstanding state or local law along the route. The protection is conditional. The person transporting the firearm must fall outside the federal prohibitions, so the provision confers nothing on a person whom federal law bars from possessing a firearm in the first place. The journey must run between two places of lawful possession, so the statute protects the passage between lawful endpoints rather than possession at a place where possession itself is unlawful. The firearm must be unloaded, and neither the firearm nor any ammunition being transported may be readily accessible during transport. A firearm carried in a condition that leaves it ready to hand falls outside the description the statute protects, because section 926A addresses transport of a firearm as an item being moved between places, not carriage of a firearm for use along the way.

The reach of section 926A is best understood through the work its notwithstanding clause performs and the work that clause does not perform. Along an interstate route, a traveler may pass through states and localities whose possession rules differ from the rules at both endpoints and might treat the mere presence of the firearm in a vehicle as an offense under local law. Section 926A displaces that layer of law for transport meeting its conditions, so a journey between two places of lawful possession does not fail in the middle. The provision ranks among the rare instances in which federal firearms law overrides state law along the route, in a statutory scheme whose general posture, expressed in section 927, is that Congress did not occupy the field and that state law stands unless a direct and positive conflict prevents the two from standing together. Section 926A creates such a displacement deliberately, for a bounded purpose, and the bounds define the provision as much as the protection does. Section 926A says nothing about carry at the destination, where possession and carry are governed by the law of the place arrived at. The provision likewise says nothing about acquisition or transfer during the journey, subjects that sections 922(a)(3), 922(a)(5), and 922(b)(3) govern through their own rules. A change of residence follows the same frame: the federal provision covers the movement itself, and the visited or newly occupied state’s possession and carry law governs from the point of arrival onward.

Carry stands apart from every question considered so far, because carrying a firearm, in the sense of bearing it accessibly on the person or in a vehicle, is conduct at a place rather than movement between places, and federal law leaves that conduct almost entirely to the states. No provision of the Gun Control Act creates a general federal permit to carry. The authority under which an ordinary person carries in a particular state comes from that state’s law. When a permit holder crosses a line between states, the permit travels as a document, but its legal effect in the state entered depends entirely on that state’s recognition rules. Recognition is a matter of each visited state’s recognition statutes and reciprocity agreements. One state may extend recognition by its own statute to permits issued by other states, or by some of them, or may rest recognition on a reciprocity agreement negotiated with the issuing state, while another state extends no recognition to the permit in question at all. The result is a patchwork in the literal sense, a pattern assembled state by state from separate statutes and separate agreements, with no single national answer to the question whether a given permit has effect in a given state. The answer in each instance sits in the law of the state entered, applied to the particular permit presented, and an answer obtained for one crossing supplies no answer for the next.

What is the one federal carry rule that crosses every state line?

The one federal carry rule is the Law Enforcement Officers Safety Act, codified at sections 926B and 926C. It allows a qualified active, retired, or separated law enforcement officer meeting its conditions to carry a concealed firearm in any state, notwithstanding state or local law, subject to statutory limits.

Congress enacted the Law Enforcement Officers Safety Act in 2004, as Public Law 108-277, and later amended the statute through Public Law 111-272 in 2010 and through section 1089 of Public Law 112-239 in 2013. The Act operates through two codified provisions that divide its covered class by service status. Section 926B addresses qualified law enforcement officers, the active category, and section 926C addresses qualified retired or separated law enforcement officers. A person carrying under the Act must meet the qualification standard the statute prescribes and must carry the prescribed identification while doing so. Those conditions travel with the person, because the federal carry authority arises from the combination of status, qualification, and identification that the statute specifies, and a person who cannot satisfy the statutory description holds no authority under the Act in any state. The firearm carried under the Act is a concealed firearm, and the authority extends to carry in any state, notwithstanding state or local law to the contrary. That notwithstanding language places the Act beside section 926A as a rare federal displacement of state firearms law, broader in one respect, because section 926A protects a firearm transported unloaded and inaccessible, while the Act addresses a concealed firearm carried on the person.

The Act’s limits are stated in the statute and form part of the rule rather than exceptions discovered outside it. The Act does not override state laws that allow private property owners to prohibit firearms on their property, and it does not override state laws that allow government entities to prohibit firearms on government property. A qualified officer carrying under the Act therefore carries under a federal authority that stops at a property line the state has empowered an owner or a government entity to defend. The Act also excludes specified categories of weapons from its coverage, namely machine guns, silencers, and destructive devices, so the federal authority attaches to an ordinary concealed firearm carried by a qualified person and not to those excluded categories in any hands. Each limit reflects the same legislative method visible across the interstate provisions: Congress identified a defined subject, displaced state law for that subject in stated terms, and left surrounding subjects where state law and other federal law had placed them. The Act consequently supplies a genuine national carry rule, uniform in the sense that its authority does not depend on the recognition statute or reciprocity agreement of the state entered, and bounded in the sense that its class, its conditions, and its exclusions are fixed by federal statute.

The boundary of the Act matters most where the Act ends, because the most persistent error in accounts of interstate carry treats the Act, or the general fact of state permit systems, as evidence of a broader federal rule that does not exist in the statutory record. No general national reciprocity statute for ordinary permit holders had been enacted by August 2021. Bills proposing national reciprocity for ordinary carry permits had been introduced in successive Congresses, and none of those proposals had become law by the article’s August 2021 date. The distinction between introduction and enactment is the whole of the point. A succession of such bills expresses a recurring proposal, but neither an introduction nor its recurrence changes the law governing a permit holder who crosses a line between states. That governing law remained, at every point through August 2021, the recognition law of each state entered. An ordinary state permit consequently derived any effect outside the issuing state from the visited state’s statutes and agreements alone. Confusing a qualified officer’s federal authority under sections 926B and 926C with an ordinary permit holder’s position collapses a distinction Congress itself drew, between a defined class of officers carrying under federal conditions and permit holders carrying under state authority. The collapse produces a single mistaken picture of national carry, uniform and federally guaranteed, in place of the divided structure the statutes actually describe.

Acquisition by a non-licensee outside the state of residence falls under the bar of section 922(a)(3), with its narrow exceptions. A private transfer to a resident of another state falls under the bar of section 922(a)(5), with its corresponding exceptions. A purchase from a licensee across a state line proceeds under section 922(b)(3), face to face for a long gun that satisfies both states’ laws, and through a home state licensee for a handgun in every case. Transport between two places of lawful possession proceeds under section 926A, on the conditions of lawful status, an unloaded firearm, and a firearm and ammunition that are not readily accessible, notwithstanding state or local law along the route. Carry at any destination, and carry anywhere by an ordinary permit holder, rests on the law of the state where the carry occurs, through that state’s own carry rules and its recognition of permits issued elsewhere. Carry by a qualified active, retired, or separated law enforcement officer rests on sections 926B and 926C, the single federal carry rule that crosses every state line, within its stated conditions and limits. Federal law thus governs the commerce and the movement, state law governs the conduct at each end of the movement, and the line between the two bodies of law runs through every interstate journey a firearm makes.

What the Tracing Research Shows, and What It Does Not Settle

Every attempt to measure movement of firearms across state lines through research on recovered firearms begins with a particular administrative record, and the character of that record limits what any finding drawn from it can establish. The Bureau of Alcohol, Tobacco, Firearms and Explosives operates a National Tracing Center that traces a recovered firearm from manufacture or import through its first retail sale. A completed trace therefore identifies the first retail purchaser and the source state in which that first retail sale occurred. A trace does not identify the person from whom the firearm was recovered as the first purchaser, and a trace does not by itself reconstruct the path that a firearm followed after the first retail sale, the hands through which the firearm passed, or the transactions, movements or thefts that intervened between sale and recovery. The distinction between first sale and recovery matters throughout the research literature, because the place of first retail sale and the place of recovery are the two fixed points that trace data supply, while the interval between those points remains largely outside the record.

A second limit concerns coverage. Only firearms that law enforcement agencies submit for tracing are traced, so traced guns form a selected subset of crime guns rather than a sample drawn to represent all firearms recovered in connection with crime. Submission practices, agency resources and investigative priorities shape the subset, and a change in the composition of submitted firearms can alter the patterns recorded in trace data without any corresponding change in the underlying movement of firearms. A third limit concerns access. Appropriations riders first enacted for fiscal 2004, known as the Tiahrt provisions, restricted disclosure and evidentiary use of trace data. Those restrictions shaped which researchers could examine the records, in what form, and for what purposes, and the limits have been part of the documented record, stated by the Bureau of Alcohol, Tobacco, Firearms and Explosives and by researchers who worked with the data. Read together, the three limits frame every finding that follows. Trace research can document associations between the state of first sale and the state of recovery across large numbers of recovered firearms, and trace research can compare those associations across places and across periods. Trace research cannot, on its own, count all firearms that crossed a state line, cannot separate deliberate movement for criminal supply from other forms of movement without additional evidence, and cannot establish by itself how much a given difference between state laws caused an observed flow.

Within those limits, a body of research examined what trace data showed about interstate patterns. Brian Knight of Brown University published a study titled State Gun Policy and Cross-State Externalities: Evidence from Crime Gun Tracing in the American Economic Journal: Economic Policy in 2013, in volume 5, issue 4, at pages 200 to 229. Knight used Bureau of Alcohol, Tobacco, Firearms and Explosives tracing data from 2009 covering 145,321 traced crime guns. About one third of those traced firearms had been first sold in a state other than the state of recovery. Knight reported that flows ran disproportionately from states whose laws Knight’s index rated less restrictive toward states whose laws the index rated more restrictive, and that flows decayed with distance between the state of first sale and the state of recovery. The largest single flow in the 2009 data ran from Indiana into Illinois, with more than one thousand guns recovered in Illinois in 2009 that had been first sold in Indiana. Knight also presented evidence that criminal gun possession was higher in states exposed to less restrictive laws in nearby states, as those laws were rated by the index constructed for the study. The same study also recorded a value on the other side of the structural question. Knight himself stated the countervailing value of decentralization, namely that decentralization permits states to tailor policy to local preferences. The study therefore linked a measured interstate pattern to differences among state laws as rated by its author, while also identifying a reason, grounded in local preference, for preserving differences among state laws rather than treating variation itself as a defect.

A different form of inquiry, an official report rather than a peer reviewed journal article, examined recoveries in a single state over a six year span. The New York Attorney General issued a report titled Target on Trafficking in October 2016. The report examined 52,915 firearms recovered by New York law enforcement from 2010 to 2015. Of the 46,514 recovered firearms with a known source state, 34,344, or 74 percent, had been first sold outside New York. Among recovered handguns, the report placed the out of state share at 86 percent. Nearly half of the out of state guns came from six states along the Interstate 95 corridor and from Ohio. Proponents of the report applied a label to the pattern described in the report, calling the corridor flow the Iron Pipeline, and the label belongs to that framing rather than to the trace records themselves. The report presented the geographic concentration as evidence of a supply pattern organized around a small number of source states, while the figures in the report, taken on the terms set by trace data, documented the state of first retail sale for recovered firearms with a known source and did not reconstruct each movement between sale and recovery.

Two further studies extended the inquiry from description of flows toward association between flows or diversions and particular categories of state regulation. Daniel Webster, Jon Vernick, Emma McGinty and Ted Alcorn contributed a chapter titled Preventing the Diversion of Guns to Criminals through Effective Firearms Sales Laws to the 2013 volume Reducing Gun Violence in America, published by Johns Hopkins University Press. Using Bureau of Alcohol, Tobacco, Firearms and Explosives trace data from fifty-four cities, the authors reported that in-state diversion, measured by short time to crime, ran two to four times higher in cities in states lacking the package of private-sale regulation, dealer oversight and purchase licensing examined in the chapter. In the authors’ reading of the literature, purchase licensing was the measure most consistently associated with lower diversion. The chapter therefore connected the speed with which firearms moved from retail sale to recovery in crime, within the state of sale, to the presence or absence of a specified set of state measures. Leo Kahane published a gravity-model analysis in the International Review of Law and Economics in 2020, in volume 61, as article 105871. Kahane examined trace data from 2010 to 2015 and found that interstate exports of crime guns, including short time-to-crime guns, were associated with differences in state regulation. The gravity-model form treated flows between states as a function of the characteristics of the paired states, including regulatory differences, and the reported association concerned exported crime guns rather than a count of all firearms transported between states.

Taken together, the four inquiries addressed related questions through different designs and on different scales. Knight examined a national set of traced crime guns in a single year and related flows between states to an index of state laws. The New York report examined recoveries in one state across six years and described the geographic concentration of source states. Webster, Vernick, McGinty and Alcorn examined diversion within the state of sale across fifty-four cities and connected diversion to a specified package of state measures. Kahane modeled flows between pairs of states across six years and related exports of crime guns to regulatory differences between the paired states. The designs share a dependence on trace records and therefore share the limits attached to those records, while differing in the comparison each design makes possible.

The findings summarized in the preceding paragraphs drew documented criticism, and that criticism receives equal care here, because a comparison that reports only findings and omits the published responses would misstate the condition of the record. The National Rifle Association’s Institute for Legislative Action responded to the New York Attorney General’s Target on Trafficking report by directing attention to time to crime. In that response, under 5 percent of the traced firearms had a time to crime under one year, and about 11 percent had a time to crime under three years. On the figures cited in the response, most recovered firearms in the New York study had passed through a longer interval between retail sale and recovery, a pattern that the response presented as inconsistent with an account centered on firearms moved across state lines shortly before recovery. A separate published critique of the report noted a different gap in the record. A retail purchase date could not be determined for 42 percent of the traces, which limited the ability to calculate time to crime across the full set of recovered firearms and limited comparisons that depend on knowing when a first retail sale occurred. The two criticisms operate on different parts of the report’s reasoning, one on the intervals that could be measured and one on the share of traces for which an interval could be measured at all, and both belong to the documented debate over what the New York figures establish.

Beyond the responses to a single report, standing methodological disputes run through the literature as a whole, and the disputes are stated here as disputes rather than as conclusions. One dispute concerns selection. Because traced guns are a selected subset of crime guns, researchers disagree about how far patterns in traced firearms can be generalized to firearms that agencies did not submit. A second dispute concerns interpretation of source state. Source state marks the first retail sale, not the route a firearm followed or the hands through which a firearm passed after sale, so researchers disagree about how much of an interstate pattern reflects movement arranged to supply criminal possession and how much reflects other processes. A third dispute is mechanical. States whose licensing regimes support few dealers record high out of state shares by structure, because a small in-state dealer base leaves fewer first retail sales to be recorded inside the state, and researchers disagree about how to separate that mechanical effect from movement driven by regulatory differences. A fourth dispute concerns contributing causes. Movement of people, theft and lawful relocation all contribute to the interstate presence of firearms, and an aggregate flow between two states combines those contributions with any deliberate trafficking that occurred. Researchers disagree on the share of the flow that is deliberate trafficking, and researchers disagree on how much any state’s crime rate responds to the laws of neighboring states. No resolution of those disputes is adopted in the sections that follow, and the structural arguments considered next proceed from the same contested record to different conclusions about institutional design.

The uniformity argument, advanced by supporters of national reciprocity and of federal floors and by state preemption advocates at the state level, begins with the experience of a lawful possessor crossing a boundary. Under a divided system, a person whose possession complies with the law of one state can enter another state whose law governs the same conduct differently, and the line that separates compliance from criminal liability can be invisible at the moment of crossing. Holders of the uniformity argument treat that exposure as a defect in the arrangement rather than as an ordinary incident of federalism, because criminal liability turns on geography that a traveler may have no practical means of perceiving and because the conduct at issue was lawful at its origin. A uniform rule, in this account, gives a single standard that a possessor can learn once and follow across jurisdictions, and uniformity removes a trap that falls on persons who had no intention of supplying firearms for crime. The second strand of the argument concerns commerce. Firearms move through a national market in manufacture, distribution and retail sale, and holders argue that commerce in a national market should run on one rulebook rather than on a collection of rulebooks of the states that a manufacturer, a distributor or a dealer must reconcile transaction by transaction. A single rulebook, in this account, lowers the cost of compliance, reduces error in the commercial channel, and places responsibility for the content of the rules on one legislature whose choices can be debated in one forum. The third strand returns to the research record. Variation among the laws of the states, holders argue, invites the cross-border flows that the research documents, because differences between neighboring regimes create the gradient along which firearms move from the state of first sale to the state of recovery. A uniform national floor, or uniform rules of the states that leave no local variation beneath them, would remove the gradient itself rather than relying on enforcement at a border that firearms cross without inspection. Supporters present uniformity as the direct institutional answer to an externality that, on the account offered by studies such as the study by Knight, one state can impose on another through the content of its own laws. The fourth strand concerns enforcement. Enforcement is simpler under uniform rules, holders argue, because an officer in any jurisdiction applies the same standard, because prosecutors and courts work from one definition of lawful and unlawful conduct, and because regulated parties cannot exploit differences between jurisdictions to place a transaction in whichever forum imposes the fewest conditions. Simplicity of that kind, in this account, is not a convenience but a condition of consistent enforcement, since a system that varies from place to place invites uneven application even among officials acting in good faith. Taken together, the strands present variation as the source of three linked harms, exposure of lawful possessors to unexpected liability, friction and error in a national commercial market, and interstate flows that carry the consequences of one state’s choices into another state, and present a uniform rulebook as the remedy that addresses all three harms at the level of design rather than through case by case enforcement after movement has occurred.

The local-control argument, advanced by home-rule advocates and by opponents of preemption, including the published position of the Giffords Law Center, begins with a difference in conditions. Conditions in dense cities differ from conditions in rural counties, in population concentration, in the settings in which firearms are carried and stored, in the demands placed on local police, and in the proximity of bystanders to any single act of violence. Holders of the local-control argument contend that a rule fitted to one setting can fit another setting badly, and that a legislature or council deciding for a single kind of community can weigh tradeoffs that a distant legislature deciding for every community at once must average away. The second strand concerns the level of government that bears the consequences. The level of government closest to the consequences should set the rules, in this account, because local officials answer to the residents who live with the results of a policy and because those officials possess knowledge of local conditions that a state or national legislature cannot reproduce through hearings alone. Accountability and knowledge point in the same direction, toward decision by the smallest unit that contains the problem, and preemption from a higher level severs the link between a decision and the electorate that experiences the decision. The third strand concerns experimentation. States and cities are where policy experiments are run, holders argue, and several statewide rules began as local ordinances, with California’s dealer rules among the examples cited in this account. A local ordinance can test a regulatory device on a limited scale, generate experience with administration and compliance, and supply a model that a state legislature can adopt, revise or reject with the benefit of a working example. Uniformity imposed from above, whether by a state preemption statute or by a federal floor that displaced local choice in the other direction, forecloses that sequence by preventing the first experiment from occurring. The fourth strand is constitutional in character. Variation is the federal design, holders argue, not a defect of the design, because the federal arrangement reserves distinct spheres to distinct levels of government and expects different communities to reach different answers to contested questions of public order. On that view, the cross-border consequences documented in trace research are a cost to be managed within a system built on divided authority, through enforcement against unlawful movement and through cooperation among jurisdictions, rather than a justification for collapsing the division itself. A system that permits variation also permits a community to accept a regulatory burden that its neighbors decline, and the freedom to differ includes the freedom to impose greater conditions on conduct within a community’s own borders. Taken together, the strands present variation as the working expression of a federal structure, present local knowledge and local accountability as positive goods rather than as obstacles to coherence, and present the harms attributed to variation as problems for enforcement against unlawful conduct rather than as grounds for transferring decisions away from the governments closest to the people governed.

The two arguments rest on the same trace record, read through the disputes that record has generated, and each argument assigns a different weight to the harms and goods that divided authority produces. The uniformity argument treats interstate flow as the central fact and local variation as the mechanism that sustains the flow. The local-control argument treats local difference in conditions as the central fact and variation as the institutional means by which different conditions receive different rules. This article adopts neither side’s empirical resolution of the disputes over selection, source state, mechanical effects and contributing causes, and the assessment that follows proceeds from the structure of the divided system itself rather than from a settled answer to the contested questions in the tracing literature. A verdict grounded in that structure can identify which layer of law supplies the operative rules for a given practical question without deciding how much of an observed interstate flow deliberate trafficking explains, and without deciding how strongly the law of one state affects the crime rate of another state. Those empirical questions remain open on the record presented in this section, and that openness forms part of the comparison, because each structural argument claims support from research whose limits, findings, criticisms and disputes have been set out in full before either argument was stated.

The Verdict: Commerce at the Federal Layer, Conduct at the State Layer

Deciding factors

The comparison resolves once the question is separated into its two parts. Federal law governs commerce, and the law of the states governs conduct. The federal part concerns the channels through which firearms enter and move in trade, the persons whom federal law bars from the market everywhere, and movement across state lines through defined routes. The state part concerns conditions attached to a purchase by a particular person, carrying in a particular place, storage in a particular home, categories permitted in a particular state, and court procedures after a protective order. A question about a dealer license, a transaction record, or a federal check belongs to the first part. A question about a purchase permit, a waiting period, a private transfer, a storage duty, or surrender belongs to the second part. A single transaction ordinarily contains elements from both parts, and an answer drawn from one layer alone leaves the other layer unexamined.

The deciding factor can be stated in the article voice without qualification. A reader’s practical rules are set by their state and by their state’s treatment of its cities; the federal layer that national debate concentrates on governs a comparatively narrow slice of the applicable law. Federal law licenses manufacturers, importers, and dealers, requires a transaction record and a federal check for licensee transfers, defines nine categories of prohibited persons in section 922(g) together with the indictment provision in section 922(n), channels interstate movement through licensees, protects defined transport in section 926A, and creates defined carry authority for qualified officers in sections 926B and 926C. Federal law enacted no general purchase permit, no general licensing of owners, no general home storage mandate, no general carry license for ordinary holders, and no surrender procedure. Each absent subject is a subject on which the law of the states, where a legislature acted, supplies the operative rule.

The law of the states supplies the operative rule on the subjects that shape ordinary experience. A state decides whether a purchaser obtains a permit in advance, whether a waiting period delays delivery, whether a private transfer requires a check or a credential, whether carry proceeds without a permit or under a license issued on objective criteria or under a license conditioned on a judgment about need or suitability, whether a firearm not in use must be locked, whether magazines above a stated capacity or specified semiautomatic firearms fall under added conditions, whether added categories of persons face a state prohibition, and whether a court may or must order surrender with proof and retrieval procedures. The law of the states also defines offenses and penalties for unlawful possession and carry. Two purchasers who face an identical federal form and check therefore face different practical law when one purchase occurs in a state with a purchase permit and a waiting period and the other occurs in a state with neither addition.

A further deciding element sits inside the states’ layer. A state decides whether its cities and counties may add rules, through express preemption statutes, limited reservations, the absence of an express statute, and in some states penalties directed at local officials. In a state with a broad express statute, a resident faces state rules on reserved subjects and no competing local rule. In a state without such a statute, a resident faces state rules and any local rule that survives conflict and implied preemption examination. Section 927 permits a state to add to federal law, and preemption doctrine inside a state determines whether a locality may add to state law. The two permissions are separate, and the second permission controls the local part of a practical answer.

Neither layer displaces the other in the ordinary case. Both layers bind at once, and conduct must satisfy every applicable condition from each layer. Federal permission for a licensee transfer after a completed check does not cancel a permit condition imposed by one of the states, and a permit from one of the states does not cancel a federal prohibition. A direct and positive conflict is the narrow exception in section 927, and the displacements in sections 926A, 926B, and 926C are specific and textual. The anti-commandeering doctrine adds an institutional boundary, because Congress may not conscript legislatures or officers of the states, while a state may decline assistance, may volunteer as a point of contact, and may not obstruct federal officers or purport to nullify federal law. The federal skeleton has one text across the country, and content differs among the states and, where local authority survives, by locality.

Recommendations by reader

For a student, the productive sequence begins with the federal skeleton and proceeds to the states’ layer. The federal skeleton is one short system, built around licensing of the commercial channel, a transaction record, a federal check, prohibited person categories, interstate channels, a transport provision, and the floor principle. A student who learns that skeleton first gains a framework into which rules of the states can be placed as additions, administrative variations, or independent regimes on subjects federal law leaves open. After the skeleton, study belongs in the states’ layer, where the operative rules live, and a comparison between two states on purchase permits, waiting periods, private transfers, carry models, storage duties, category definitions, and protective order procedures teaches the division efficiently. A structured place for that comparison appears in the US legislation study guide.

For a legislative staffer, attention belongs in legislatures of the states and in preemption bills. A change in a state purchase permit, waiting period, private transfer rule, carry model, storage duty, or category definition alters practical law for residents of that state without any change in federal law, and a preemption bill alters practical law by changing who may decide rather than by changing a substantive rule directly. A staffer therefore gains more from a statehouse calendar, a committee substitute on a permit provision, or a repeal of a preemption statute of the kind enacted in Colorado in June 2021 than from a federal proposal at introduction without enactment. Federal monitoring retains a defined place, centered on amendments to chapter 44, changes in prohibited categories, and proposals on national reciprocity or transport.

For a researcher, work belongs at the level of the states, and trace data belongs inside the limits documented for that record. Work at the level of the states means building datasets from statutes of the states, counting states only with a named source and a date attached to each count, keeping paired counts separate when definitions differ, and recording definitions alongside totals because category and magazine counts turn on statutory wording. A trace identifies a first retail purchaser and a source state, covers only firearms submitted for tracing, and carries disclosure limits imposed through appropriations riders first enacted for fiscal 2004. Findings about flows, associations with regulatory differences, and disputes over selection, mechanical effects, theft, relocation, and deliberate trafficking sit inside those limits, and stating the limits in every publication protects findings from claims that the record cannot carry.

For a journalist, the statehouse check precedes the congressional check on any practical question. A report about whether a purchase requires a permit, whether a carrier requires a license, whether a city may enforce an ordinance, or whether a court ordered surrender turns on a state statute, a state preemption provision, or a state court procedure, and a federal source answers only the federal part. Precision about sources and dates carries particular weight, because counts change when legislatures act, because a 2019 administrative report describes 2019 arrangements, and because a statute enacted in June 2021 for a September 2021 effective date describes a different position from a statute in effect on August 1, 2021. Reporting that holds those distinctions gives readers the layer, the jurisdiction, and the date behind every rule described.

The Who-Decides Table

Subject	Federal law	State law	May localities add requirements?
Licensed dealer purchase	License required; transaction record and federal check required	Added permit or waiting conditions vary by state	Generally no on reserved subjects; depends on state preemption law
Private transfer between state residents	No federal check for a transfer between unlicensed residents of one state	Check or credential requirement varies by state	Generally no on reserved subjects; depends on state preemption law
Who may not possess	Nine prohibited categories plus persons under indictment	Added categories and state offenses vary by state	Generally no on reserved subjects; depends on state preemption law
Purchase permit	No federal purchase permit for individuals	Permit required only where state law creates a permit	Generally no on reserved subjects; depends on state preemption law
Waiting period	No general federal waiting period in the federal check system described	Period required only where state law imposes a period	Generally no on reserved subjects; depends on state preemption law
Carry in public	No general federal carry license for ordinary holders	Permitless, objective licensing, or discretionary licensing by state	Generally no on reserved subjects; depends on state preemption law
Carry across state lines	Defined authority for qualified officers; no general reciprocity for ordinary holders	Recognition statutes and agreements of each state entered	No; recognition is a matter of state law
Firearm categories and magazines	No federal category ban in force at the August 2021 date	Restrictions and definitions vary by state	Generally no on reserved subjects; depends on state preemption law
Home storage	Device provided by a licensee with a handgun transfer; no general home mandate	Locking and child access duties vary by state	Generally no on reserved subjects; depends on state preemption law
Protective orders and surrender	Prohibition defined for qualifying orders and domestic violence misdemeanors	Surrender, proof, retrieval, and temporary removal procedures vary by state	Generally no on reserved subjects; depends on state preemption law
Local ordinances	No general federal rule allocating authority between a state and its cities	Express preemption, limited preemption, or no express statute by state	The answer is set by state preemption law itself

Closing the Comparison

The comparison ends where the opening began, with two layers operating at the same time and a third, local layer whose presence depends on the law of the states. Federal law licenses commerce, defines prohibited persons with national uniformity, channels interstate movement through licensees, protects defined transport between places of lawful possession, and creates a defined carry authority for a qualified class of law enforcement officers. The law of the states governs conduct, through purchase permits, waiting periods, private transfer rules, carry licensing or the absence of a carry license requirement, storage duties, category and magazine definitions, added prohibitions, and protective order procedures. Section 927 holds the arrangement together by treating federal law as a floor rather than a ceiling, subject to a narrow exception for a direct and positive conflict. State preemption law then decides whether a city or county may add a rule on a subject that state law governs, and the anti-commandeering doctrine decides the separate institutional question by barring Congress from conscripting legislatures and officers of the states while leaving federal enforcement to federal personnel. A practical question about firearms law therefore receives a complete answer only after the federal layer, the states’ layer, and the local position under the law of the states have each been examined in turn, and the states’ layer supplies the larger part of most practical answers.

The disclaimer stated in the opening applies with equal force at the close. The article is general information about the structure of firearms law in the United States. The article is not legal advice, and the article states no obligations for any person under the law of any state. Obligations depend on the jurisdiction concerned and on facts specific to an individual case, and no passage in the comparison substitutes for the text of a governing statute or for advice addressed to a particular situation. Description of a mechanism, a count, a procedure, or a research finding is description of legal structure and of a documented record, presented so that a student, a staffer, a researcher, or a journalist can locate the layer that made a rule and the source that supports a statement about that rule. For study organized around the division, a reader may keep your statute notes, citations, and case chronologies together free on VaultBook as the comparison is worked through section by section. For revision of the government structure behind the comparison, a reader may practice and revise US government and civics material on ReportMedic alongside attention to the state code that governs conduct in the jurisdiction under examination. The division itself remains the central lesson after every detail is set aside. Commerce sits at the federal layer, conduct sits at the states’ layer, local authority sits where state law places local authority, and both principal layers bind at once.

Frequently Asked Questions

Q: Does federal firearms law set a floor or a ceiling?

Federal firearms law operates as a floor rather than a ceiling. Section 927 of title 18 states that no provision of chapter 44 is to be construed as indicating an intent by Congress to occupy the field, to the exclusion of state law on the same subject, unless a direct and positive conflict makes the two impossible to reconcile. A state may therefore forbid or condition conduct that federal law permits, and both layers bind at once. A state permit, a waiting period, or an added prohibition creates no conflict because compliance with both layers remains possible. Specific federal provisions displace state law in defined settings, including interstate transport and carry by qualified officers, and conflict preemption remains available where compliance with both commands is impossible.

Q: Which transactions does federal firearms law not reach?

Federal firearms law does not reach an intrastate private transfer with a federal check or a federal transaction record. The check in section 922(t) and the record on Form 4473 attach to licensee transfers, and a transfer between unlicensed residents of the same state proceeds under federal law without that machinery, although federal prohibitions on possession bind the parties as substantive law. Federal law also enacted no general purchase permit for individuals, no general licensing of owners, and no general mandate for storage in a home. Interstate private transfers stand on the other side of the line. Sections 922(a)(3) and 922(a)(5) bar acquisition and transfer across state lines between nonlicensees outside narrow exceptions, including bequests, intestate succession, and temporary sporting loans.

Q: How many states require checks on private sales under firearms law?

Two documented counts answer the question in different ways because the counters asked different questions. The Giffords Law Center counted twenty states and the District of Columbia requiring a background check for transfers of at least some firearms between private parties, measuring states that required a check at the point of the private transfer itself. The Center for American Progress, in a February 2021 fact sheet, counted twenty-two states and the District of Columbia under a broader measure that included permit to purchase systems reaching private sales. In a permit system counted under the broader measure, screening occurred through a credential obtained in advance rather than through a separate check between the parties at transfer. The gap of two states reflects methodology before geography.

Q: Can cities regulate more strictly than state firearms law?

Whether a city may regulate beyond state law depends on the preemption law of the state in which the city sits. The Giffords Law Center taxonomy identified five states with no express statute preempting local firearms regulation, two states with limited express preemption, and forty three states with express statutes preempting all or substantially all local firearms and ammunition regulation. In a state in the third group, a local ordinance on a reserved subject is displaced by the state statute. In a state without an express statute, a city has more room, although conflict preemption and implied preemption confine local law. Research reported in May 2021 also documented punitive provisions in a group of states, attaching penalties to local officials who enacted or enforced displaced ordinances.

Q: Can the federal government make states enforce firearms law?

The federal government may not make a state enforce federal firearms law by command. In New York v. United States in 1992, the Supreme Court held that Congress may not compel a state legislature to enact a federal program. In Printz v. United States in 1997, the Court invalidated the interim Brady command directing chief law enforcement officers to conduct checks, together with an implied duty to accept completed forms, while leaving licensee duties, the waiting period, state alternative systems, and the forthcoming federal system intact. In Murphy in 2018, the Court held that Congress may not order a state legislature to maintain a prohibition. A state may decline assistance or volunteer as a point of contact, and a state may not obstruct federal officers or purport to nullify federal law.

Q: Is there federal carry reciprocity in firearms law?

Federal law contains no general carry reciprocity for ordinary permit holders at the August 2021 date. Bills proposing national reciprocity were introduced in successive Congresses, and none had been enacted by August 2021. Recognition of an ordinary permit in a state other than the issuing state depends on the recognition statutes and reciprocity agreements of the state entered. A federal carry authority does exist for a defined class. The Law Enforcement Officers Safety Act, codified in sections 926B and 926C, permits a qualified active, retired, or separated law enforcement officer who carries prescribed identification and meets the qualification standard to carry a concealed firearm in any state, subject to limits for private and government property and exclusions for machine guns, silencers, and destructive devices.

Q: Do guns move from weak law states to strict ones under firearms law?

Trace research documented movement between states of first sale and states of recovery, and researchers disputed the magnitude and meaning of that movement. Brian Knight, using tracing data from 2009 covering 145,321 traced crime guns, reported that about one third had been first sold in a state other than the state of recovery, and reported flows disproportionately from states whose laws Knight’s index rated less restrictive toward states whose laws the index rated more restrictive. The New York Attorney General reported in October 2016 that 74 percent of recovered firearms with a known source state had been first sold outside New York. Critics cited time to crime figures and missing purchase dates, and researchers disputed selection effects, mechanical effects, and the share attributable to deliberate trafficking. No resolution is adopted in the documented record.

Q: Which should a student study first, federal or state firearms law?

A student benefits from studying the federal layer first and the state layer second. The federal layer is one short system, covering licensing of manufacturers, importers, and dealers, a transaction record and a federal check for licensee transfers, prohibited person categories, interstate transfer channels, a transport provision, and the floor principle in section 927. Study of that skeleton gives a framework for placing state rules. The state layer then supplies the operative rules on purchase permits, waiting periods, private transfers, carry, storage, category definitions, and protective order procedures. A student who reverses the sequence learns the detail of one state without a reliable method for separating national elements from state elements, and comparative study across two states after the federal skeleton teaches the division directly.

Q: What does section 927 of the federal firearms chapter say about state law?

Section 927 of title 18 addresses the relationship between chapter 44 and state law on the same subject. The provision states that no provision of chapter 44 is to be construed as indicating an intent on the part of Congress to occupy the field in which the provision operates, to the exclusion of state law, unless a direct and positive conflict exists between the federal provision and state law so that the two cannot be reconciled or consistently stand together. Congress added the provision through Public Law 90-351 in 1968, and Public Law 90-618 amended the provision. The section negates field occupation and leaves conflict preemption intact, so a state may add conditions that federal law omits while a state law that makes federal compliance impossible falls in the particular case.

Q: What is state preemption of local firearms ordinances?

State preemption of local firearms ordinances is a state rule that displaces local regulation on a subject. Express preemption rests on statutory language reserving a subject to the state or declaring local ordinances on the subject void. Implied preemption rests on a conclusion that a comprehensive state scheme leaves no room for a local rule or that a local rule conflicts with a state rule. The Giffords Law Center taxonomy sorted states into five with no express preemption statute, two with limited express preemption, and forty three with express statutes preempting all or substantially all local firearms and ammunition regulation. Punitive preemption adds penalties directed at local officials, a form documented in research reported in May 2021 as present in fifteen states in 2018, up from two states in 2009.

Q: Which law governs a firearm carried across a state line?

Several bodies of law govern different parts of a crossing, and no single provision governs the whole journey. Federal law in sections 922(a)(3), 922(a)(5), and 922(b)(3) governs acquisition, private transfer, and licensee sales across state lines. Federal law in section 926A governs transport between two places where possession is lawful, on conditions that the person is not otherwise prohibited, the firearm is unloaded, and neither the firearm nor ammunition is readily accessible. Possession and carry at the destination are governed by the law of the state arrived at, including that state recognition of a carry permit issued elsewhere. Carry by a qualified law enforcement officer is governed by the federal authority in sections 926B and 926C, within statutory conditions and limits.

Q: What does the federal safe passage provision protect during interstate travel?

The federal safe passage provision is section 926A of title 18, enacted as part of the Firearms Owners’ Protection Act of 1986. The provision protects transport of a firearm for a lawful purpose from a place where a person may lawfully possess and carry the firearm to another place where possession and carry are likewise lawful, notwithstanding state or local law along the route. Protection is conditional. The person must not be otherwise prohibited, the journey must run between lawful endpoints, the firearm must be unloaded, and neither the firearm nor ammunition being transported may be readily accessible. The provision addresses passage through intervening jurisdictions. The provision does not govern carry at a destination, acquisition during a journey, or transfer during a journey, and destination law governs conduct after arrival.

Q: How do point of contact states run the federal check differently?

In a point of contact state, a state agency stands between licensees and the federal check system, receives dealer inquiries, and returns results through the federal process, rather than licensees contacting the Federal Bureau of Investigation directly for every inquiry. The Federal Bureau of Investigation’s NICS Operations Report for 2019 recorded thirteen states acting as full points of contact. The same report recorded four states as partial points of contact for handguns, Maryland, New Hampshire, Washington, and Wisconsin, and three states as partial points of contact for handgun permit transactions, Iowa, Nebraska, and North Carolina. In partial arrangements, the state agency handled a defined slice of traffic and the remainder went to the Federal Bureau of Investigation directly. Participation rests on a state decision rather than a federal command.

Q: Who decides whether a permit is required to purchase a firearm?

State law decides whether a permit is required to purchase a firearm. Federal law requires a license for a dealer, a transaction record, and a federal check for a licensee transfer in every state, and federal law requires no purchase permit for an individual buyer. A count published by the Johns Hopkins Center for Gun Policy and Research in 2020 listed nine states and the District of Columbia requiring a license or permit to purchase at least handguns, some for all firearms, with Illinois included through the Firearm Owner’s Identification card. House File 756 in Iowa, signed on April 2, 2021 and effective on July 1, 2021, made the Iowa handgun purchase permit optional, leaving eight states and the District of Columbia with a mandatory purchase permit at least for handguns at the August 2021 date.

Q: Can a state prohibit additional categories of people from possessing firearms?

A state may prohibit additional categories of persons from possessing firearms under state law. The federal list in section 922(g) sets nine categories covering matters including a felony conviction, a qualifying protection order, and a misdemeanor crime of domestic violence, together with persons under indictment under section 922(n). That list operates as a national floor. A state may add categories, attach a state prohibition to additional offenses, and define duration and restoration under state rules, and a state defines offenses and penalties for unlawful possession under state law. Addition operates in one direction. A state may not remove a federal category, narrow a federal category, or authorize possession by a person covered by an unrelieved federal prohibition, and a state permit does not cure a federal disqualification.

Q: How do state storage requirements for firearms differ?

State storage requirements differ in scope, trigger, and design. Federal law contributes a transaction point requirement in section 922(z), under which a licensee provides a secure gun storage or safety device with each handgun sale, delivery, or transfer, subject to statutory exceptions, and federal law imposes no general home storage mandate. According to the Giffords Law Center, Massachusetts was the only state requiring every firearm, when not in use or under the owner’s control, to be secured in a locked container or fitted with a tamper resistant locking device. A tally compiled by the Giffords Law Center and reported in 2019 counted twenty seven states and the District of Columbia with child access prevention laws of varying strength, ranging from liability after a child gained access to liability where access was merely likely.

Q: Does a carry permit from one state have to be honored by another state?

A carry permit from one state does not have to be honored by another state as a matter of federal law. No general federal reciprocity statute for ordinary permit holders had been enacted by August 2021, despite introduction of reciprocity bills in successive Congresses. Effect for a permit outside the issuing state comes from the visited state, through a recognition statute extending recognition to permits from other states or through a reciprocity agreement between states. One state may recognize a permit, another state may recognize permits from a defined list, and another state may extend no recognition to the permit presented. A separate federal rule governs a defined class, because qualified law enforcement officers carry under sections 926B and 926C in any state within statutory conditions, and that federal authority does not extend to ordinary permit holders.

Q: What does firearm tracing data show about interstate movement?

Firearm tracing data record the path of a recovered firearm from manufacture or import through a first retail sale. The Bureau of Alcohol, Tobacco, Firearms and Explosives National Tracing Center identifies a first retail purchaser and a source state, and only firearms submitted by law enforcement are traced, so traced firearms form a selected subset rather than a representative sample. Brian Knight used data from 2009 covering 145,321 traced crime guns and reported that about one third had been first sold in a state other than the state of recovery, with the largest single flow from Indiana into Illinois at more than one thousand guns. Leo Kahane, using data from 2010 to 2015, found interstate exports of crime guns associated with differences in state regulation. Interpretation of source state, selection, and causation remained disputed among researchers.

Q: Which level of government restricts categories of firearms by their features?

At the August 2021 date, category restrictions operated at the state level, because no federal category ban was in force after the federal statute enacted in 1994 expired by its own terms in 2004. A compilation published in June 2020 recorded nine states and the District of Columbia restricting magazines above a capacity limit, generally at ten rounds with Colorado at fifteen rounds, and recorded seven of those states also restricting specified semiautomatic firearms, as the District of Columbia also did. A survey published in Law and Contemporary Problems in 2020 counted six states plus the District of Columbia banning assault weapons generally in 2019, with Hawaii reaching assault pistols. State definitions differed from the expired federal definition and from each other, so totals depend on source, date, and statutory wording.

Q: What should a student remember about the federal and state division for an exam?

A student preparing for an examination benefits from holding four propositions together. Federal law governs commerce, through dealer licensing, transaction records, a federal check, prohibited person categories, and interstate channels. State law governs conduct, through purchase permits, waiting periods, private transfer rules, carry models, storage duties, category definitions, and protective order procedures. Both layers bind at once under the floor principle in section 927, so federal permission does not cancel a state condition and a state credential does not cancel a federal prohibition, apart from specific federal displacements and a narrow conflict exception. Inside a state, preemption law decides whether local government may add rules, and the anti-commandeering doctrine bars Congress from conscripting state legislatures and officers while leaving federal enforcement to federal personnel.