On March 26, 2025, the Supreme Court issued an opinion in Bondi v. VanDerStok upholding a 2022 rule promulgated by the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) that targeted certain unmarked firearms, along with kits of their constituent parts, sometimes referred to as ghost guns. The rule had been challenged under the Administrative Procedure Act on the grounds that ghost guns fell outside the scope of the Gun Control Act, thus making the rule facially inconsistent with that act. Writing for a seven-Justice majority, Justice Neil Gorsuch concluded that the Gun Control Act covered at least some weapons parts kits regulated by the ATF rule and, therefore, the ATF rule was consistent with the statute even if a particular parts kit might fall outside of the rule or statute's scope.
This Sidebar provides background on unmarked firearms and weapons parts kits (i.e., ghost guns), as well as the Gun Control Act and the relevant ATF rule. It then analyzes the Supreme Court's decision in VanDerStok and concludes with considerations for Congress applicable to ghost gun regulation and firearms regulation more broadly.
Federal law, including the Gun Control Act, regulates entities licensed to engage in the firearms business (federal firearms licensees, or FFLs). Among the requirements imposed on these businesses, FFLs must "identify by means of a serial number engraved or cast on the receiver or frame of the weapon" each firearm manufactured in, or imported into, the United States. Existing regulations establish more detailed requirements for how the serial number must be affixed, including the minimum depth and print size, and require additional information such as the firearm model, the firearm caliber or gauge, and the FFL's name and business location.
Not all weapons in the United States are subject to the identification requirements described above. First, these marking requirements apply to "each firearm" manufactured or imported by FFLs. As a result, the statutory definition of the term firearm determines, in part, which articles are subject to these rules. The Gun Control Act defines firearms broadly to include, among other things, "any weapon (including a starter gun) which will or is designed to or may readily be converted to expel a projectile by the action of an explosive" and "the frame or receiver of any such weapon." These two provisions together encompass more than completed, functional firearms because they apply to an unfinished weapon which "may readily be converted" to functional as well as certain components (i.e., the "frame or receiver") of such a weapon. The terms frame and receiver are not defined in statute. As described by ATF, frames or receivers are "the primary structural components of a firearm to which fire control components are attached."
Second, the requirements apply only to FFLs, meaning that individuals who wish to make their own firearms for personal use need not identify or mark them. The process of making one's own firearm that is not subject to identification requirements has been facilitated in recent years by technological advances such as 3D printing and the commercial availability of "parts kits" that include firearm components and tools with which a functional weapon can be completed and assembled relatively quickly and easily. Some of these parts kits may include certain unfinished frames or receivers—sometimes referred to as "blanks," "billets," "castings," "machined bodies," or "80%" receivers—that ATF has not previously considered to have reached a stage of manufacturing that would make them subject to federal requirements such as interstate commerce restrictions, background checks, or marking obligations. Such components have been sold commercially, individually or in parts kits, without needing to meet such requirements.
The firearm identification requirements in statute and regulation facilitate ATF's ability to trace firearms that are lost or used in crimes, as the chain of custody and distribution may be established using an FFL's required records. Privately made firearms that enter the stream of commerce without markings useful in tracing them, and that are subsequently used illicitly, are sometimes referred to as ghost guns. ATF and other law enforcement authorities have expressed concern that the commercial availability of parts kits with unmarked, unfinished firearm frames or receivers, which also may be considered ghost guns, could facilitate access to firearms by persons prohibited from possessing them, given that such kits can be sold without a background check. Conversely, others have suggested that the importance of serial numbers in firearm tracing is overstated and that additional marking requirements would be onerous and unnecessary.
In response to developments in firearms technology and perceived gaps in the then-existing regulatory scheme, ATF issued a new final rule in April 2022 to make changes to the current regulatory definitions and requirements relevant to homemade and unmarked firearms. First, the rule amends ATF's regulatory definition of frame or receiver. The rule updates the regulatory definitions with separate sub-definitions for handgun frames, non-handgun receivers, and mufflers or silencers to clarify which part of each item will be considered either the frame or receiver, providing specific examples and pictures. Most existing ATF classifications of particular parts as frames or receivers are grandfathered in and will continue to be considered frames or receivers, as they were classified prior to publication of the rule. The new rule also expressly provides for how to mark for identification a "multi-piece frame or receiver," meaning a frame or receiver "that may be disassembled into multiple modular subparts." Under the rule, "the modular subpart that is the outermost housing or structure designed to house, hold, or contain" certain other components is the subpart of a multi-piece frame or receiver that must be identified.
With respect to firearm component kits and unfinished frames or receivers, the rule first amends the regulatory definition of firearm to include a "weapon parts kit that is designed to or may readily be completed, assembled, restored, or otherwise converted to expel a projectile by the action of an explosive."
Regulatory definitions of frame or receiver also now include "a partially complete, disassembled, or nonfunctional frame or receiver, including a frame or receiver parts kit, that is designed to or may readily be completed, assembled, restored, or otherwise converted to function as a frame or receiver." Articles that have "not yet reached a stage of manufacture" where they are "clearly identifiable as" unfinished component parts of weapons (such as unformed blocks of metal or raw materials) are excluded.
The term readily is further defined as a "process, action, or physical state that is fairly or reasonably efficient, quick, and easy" (though not necessarily the most efficient, fastest, or easiest), and includes other factors such as the expertise and equipment required, parts needed and ease of acquiring them, scope, feasibility, and expense.
Among other things, persons seeking ATF classification of a partially complete, disassembled, or nonfunctional item or parts kit to determine whether it meets the new regulatory definitions must also include any associated templates, jigs, molds, equipment, tools, instructions, guides, or marketing materials that are made available by the seller. ATF, in turn, may consider the included information or associated items in determining whether the submitted item or kit is a "frame or receiver." Additionally, the rule provides that classification decisions made before the rule's publication that particular partially complete, disassembled, or nonfunctional frames or receivers, including parts kits, did not constitute or include frames or receivers are no longer valid.
In addition to these new or amended definitions, the rule adds requirements and clarifying language to facilitate the identification and tracing of parts kits, frames or receivers, and unmarked firearms that may come into an FFL's inventory. FFLs must comply with recordkeeping requirements, including maintaining certain information (e.g., model and serial number) about the firearms that FFLs possess, receive, or dispose of, as well as completing records of firearm transactions with unlicensed persons. The rule adds express requirements for marking otherwise unmarked firearms when received by an FFL; it also requires FFLs to mark, or supervise the marking of, the frame or receiver of each "privately made firearm" that an FFL acquires within seven days of acquisition or prior to further transfer, whichever is sooner. Privately made firearms acquired before the effective date of the rule must be marked within 60 days of the effective date or prior to final disposition, whichever is sooner. The term privately made firearm is defined as a "firearm, including a frame or receiver, completed, assembled, or otherwise produced by a person other than a licensed manufacturer, and without a serial number placed by a licensed manufacturer at the time the firearm was produced." To facilitate access to marking, the rule amends certain regulatory terms to permit gunsmiths to provide professional marking services for privately made firearms. Additionally, the rule makes amendments to the regulations regarding FFL recordkeeping to clarify when and how, among other things, privately made firearms received in an FFL's inventory are to be recorded. The rule also requires maintenance of FFL records indefinitely for tracing purposes (rather than the previously required 20 years).
After the ATF issued the new rule but before it went into effect, several gun manufacturers and gunsmiths, among others, filed a lawsuit challenging ATF's authority to issue this rule under the Administrative Procedure Act, which permits legal challenges to final agency actions that are not in accordance with law. The plaintiffs argued that the ATF rule conflicted with the Gun Control Act because the revised regulatory definitions of firearm and frame or receiver were broader than the statutory meanings of those terms. (The other aspects of the ATF rule discussed above were not challenged in this lawsuit.) The trial court agreed with the challengers and issued an order vacating the ATF rule. The U.S. Court of Appeals for the Fifth Circuit affirmed the trial court's determination that these regulatory definitions contravened the statutory text of the Gun Control Act but remanded the case to the trial court for further consideration of whether to vacate the entire ATF rule rather than only the two portions of the rule challenged in the case. The government petitioned the Supreme Court for review, and the Supreme Court agreed to hear the case on April 22, 2024. The Court heard oral argument on October 8, 2024, and issued its opinion reversing the Fifth Circuit on March 26, 2025.
Seven members of the Supreme Court, in an opinion written by Justice Gorsuch, agreed that the ATF definitions of firearm and frame or receiver were facially consistent with the Gun Control Act and thus lawfully promulgated.
First, the majority concluded that the ATF definition of firearm, which includes a "weapon parts kit that is designed to or may readily be completed, assembled, restored, or otherwise converted to expel a projectile by the action of an explosive," was consistent with the Gun Control Act's definition of firearm, which includes "any weapon (including a starter gun) which will or is designed to or may readily be converted to expel a projectile by the action of an explosive." The majority analyzed whether any weapons parts kits covered by the regulation could be considered a "weapon" that "may readily be converted to expel a projectile by the action of an explosive" within the meaning of the statute. The Court determined that "weapon" was an "artifact noun" (an object created by humans usually "characterized by an intended function," rather than by "some ineffable 'natural essence.'"). As such, the term encompassed unfinished weapons when the intended function of the unfinished objects was obvious. Under this interpretation, the Court held that at least some weapons parts kits were "weapons." The Court next concluded that at least some weapons parts kits met the "readily converted" standard, finding that some kits could be made operable with comparable time and effort to starter guns, which are explicitly covered by the Gun Control Act.
Second, the Court determined that the new ATF definitions of frame or receiver, which include a partially complete frame or receiver, were consistent with the Gun Control Act's undefined usage of those terms. Here again, the majority held that frame and receiver were artifact nouns that would naturally be read to include some partially complete frames and receivers. The Court reasoned that the Gun Control Act's serialization requirements would make little sense if applied only to completed frames and receivers.
Throughout the opinion, the majority emphasized that they were rejecting only a facial challenge—that is, a claim that the regulatory definitions were inconsistent with the statute in all applications. The Court left open the possibility that some particular weapons parts kits or unfinished frames or receivers may fall outside the scope of the Gun Control Act's reach but held that, ultimately, the plaintiffs in this case did "not challenge ATF's new rule as applied to particular products."
Finally, the majority rejected application of the rule of lenity or constitutional avoidance principles because "'text, context, and structure' decide the case."
Justices Sotomayor, Kavanaugh, and Jackson issued separate concurring opinions, and Justice Thomas, joined by Justice Alito, dissented. Justice Sotomayor wrote to argue that the majority opinion would not cause undue regulatory uncertainty. Justice Kavanaugh also wrote a concurrence to highlight issues related to mens rea—the intent element of a crime—that apply to violations of the Gun Control Act in these circumstances. Justice Jackson's one-page concurrence emphasized her view that agencies maintain discretion to regulate within statutory bounds.
Justice Thomas argued in dissent that the ATF regulatory definitions exceeded the scope of the Gun Control Act. First, he argued that the "ordinary meaning of 'frame or receiver' does not include objects that may be 'converted' into a frame or receiver," contrasting the statutory definition of firearm, which includes items that may be converted to a functional firearm, with the lack of comparable language describing frame or receiver. Second, he rejected the majority's reasoning upholding the ATF definition of firearm, contending that weapons parts kits do not constitute "weapons" within the meaning of the Gun Control Act. He concluded by arguing that even if the Gun Control Act might encompass the broadened ATF definitions, the rule of lenity should favor rejecting the regulations in favor of the narrower statutory interpretation.
VanDerStok is the second case in consecutive Supreme Court terms in which the Court examined the consistency of an ATF regulation with a governing statute. Together with the prior term's decision in Garland v. Cargill (which struck down the ATF "bump stock" rule as exceeding the scope of the National Firearms Act), VanDerStok demonstrates the primacy of statutory text in determining the scope of an agency's regulatory authority. Particularly following the Supreme Court's recent decision in Loper Bright Enterprises v. Raimondo, in which the Court overturned a prior decision requiring deference to reasonable agency interpretations of ambiguous statutes, it appears that disputes like the one in VanDerStok generally will turn on judicial analysis of the precise statutory language at issue.
As a result, Congress has the authority to confirm, alter, or reverse the outcome in VanDerStok through legislation. For example, Congress may, if it wishes, amend the existing definitions in 18 U.S.C. § 921 in response to the Supreme Court's VanDerStok decision to clarify what, if any, partially complete firearms fall within the statute's scope.