“Readily Convertible” and Artifact Nouns: The Supreme Court Confirms the GCA Reaches Some Weapon Parts Kits and Unfinished Frames

Commentary on Bondi v. Vanderstok, 604 U.S. ___ (2025)

Introduction

In Bondi v. Vanderstok, the U.S. Supreme Court confronted whether the Gun Control Act of 1968 (GCA) extends to modern “ghost gun” products—weapon parts kits and unfinished frames or receivers—sold in forms that allow rapid completion into operable firearms. The petitioners (the Attorney General and federal officials) defended a 2022 Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) rule interpreting “firearm” to include certain parts kits “designed to or [that] may readily be completed, assembled, restored, or otherwise converted” to fire, and to include “partially complete” frames or receivers that can similarly be finished to function. The respondents (Jennifer Vanderstok and others, including manufacturers and hobbyists) argued that the GCA’s text cannot reach such items and secured a favorable ruling below vacating the rule.

The Court, in an opinion by Justice Gorsuch joined by the Chief Justice and Justices Sotomayor, Kagan, Kavanaugh, Barrett, and Jackson, reversed the Fifth Circuit. It held that the challenged ATF provisions are not facially inconsistent with the GCA because the statute’s definition of “firearm” plainly reaches at least some weapon parts kits and some unfinished frames or receivers. The Court emphasized the statute’s language, structure, and context—especially Congress’s inclusion of “starter guns” and the phrase “may readily be converted”—and relied on ordinary-language usage of artifact nouns (“weapon,” “frame,” “receiver”) to encompass certain unfinished items whose function is clear and quickly achievable.

At the same time, the Court stressed the narrowness of its posture: this was a pre-enforcement, facial challenge. It did not decide whether ATF may lawfully apply the rule to every product on the market, nor did it resolve line-drawing questions about how incomplete a kit or component may be and still qualify. Concurring opinions addressed compliance clarity and mens rea protections; dissents argued the Court improperly adopted a facial-challenge lens and departed from the GCA’s text.

Summary of the Opinion

• The Court held that ATF’s 2022 definitions of “firearm” (27 C.F.R. §478.11) and “frame or receiver” (27 C.F.R. §478.12(c)) are not facially inconsistent with the GCA, 18 U.S.C. §921(a)(3). It reversed and remanded.
• Weapon parts kits: Some kits plainly qualify as “any weapon … which will or is designed to or may readily be converted to expel a projectile by the action of an explosive,” §921(a)(3)(A). The Court highlighted Polymer80’s “Buy Build Shoot” kit that contains all components and was assembled in 21 minutes using common tools.
• Partially complete frames/receivers: Some unfinished frames or receivers fall within §921(a)(3)(B) (“the frame or receiver of any such weapon”). The Court pointed to a Polymer80 Glock-variant frame requiring minutes of work (removing tabs, drilling pin holes) to become fully functional.
• Limits acknowledged: Not all kits or unfinished items will qualify; the statute does not sweep in raw material or products “so far from finished” that they cannot fairly be described as weapons, frames, or receivers. But because at least some are covered, the facial challenge fails.
• Statutory tools: The Court relied on ordinary meaning, context (including Congress’s express treatment of starter guns and §923(i)’s serialization command), and longstanding agency practice as evidence of meaning, while emphasizing courts’ duty to interpret statutes independently.
• Doctrines declined: The rule of lenity and constitutional avoidance do not apply where text, context, and structure resolve the question. Concerns about unintended National Firearms Act (NFA) consequences (e.g., AR-15 receivers as “machinegun receivers”) were rejected in light of the government’s representation and the different statutory schemes.

Analysis

Precedents and Authorities Cited and Their Roles

• Abramski v. United States (2014): Cited for the GCA’s dual aims: background checks to keep guns from prohibited persons and serialization/recordkeeping to aid crime investigation. It grounds the public-safety context informing Congress’s broad definition of “firearm.”
• INS v. National Center for Immigrants’ Rights (1991): Quoted for the proposition that a regulation not invalid in all its applications is not facially invalid. The Court expressly refrained from deciding whether a Salerno-like standard controls APA facial challenges, taking the parties’ framing as given.
• Azar v. Allina Health Services (2019): Used for the interpretive canon that a term generally carries a consistent meaning within a statute—a key move in reading “frame or receiver” coherently across §§921(a)(3)(B) and 923(i).
• Loper Bright Enterprises v. Raimondo (2024): Quoted to underscore that courts exercise independent judgment in determining statutory meaning, while an agency’s longstanding and consistent view can be evidence of that meaning. The Court’s analysis does not rest on deference.
• Van Buren v. United States (2021): Cited to explain that lenity and avoidance are inapplicable when text, context, and structure provide a clear answer.
• Wisconsin Central Ltd. v. United States (2018): For the baseline rule that statutory terms are interpreted consistent with ordinary meaning.
• United States v. Mullins (8th Cir. 2006); United States v. Hall (4th Cir. 1968); United States v. 16,179 Molso … Starter Guns (2d Cir. 1971): These decisions describe starter guns and their conversion, forming the Court’s benchmark for “readily converted”—less than an hour with common tools by a person without specialized knowledge.
• Stokeling v. United States (2019): Used illustratively to show that certain criminal-statute applications (e.g., possession “in furtherance of” a crime of violence) can sensibly extend to weapon parts kits in some scenarios.
• Cutter v. Wilkinson (2005); Ohio v. EPA (2024): Cited to explain the Court’s decision not to resolve issues neither pressed nor passed upon, and to caution against raising new theories on remand.

Legal Reasoning

The majority’s analysis turns on two textual anchors and a pragmatic comparison:

• Artifact nouns and ordinary usage: The Court treats “weapon,” “frame,” and “receiver” as artifact nouns—terms denoting human-created objects whose identity often turns on intended function. In ordinary speech, such nouns sometimes refer to unfinished items when function is clear and only modest steps remain (e.g., a disassembled rifle is still a weapon; an IKEA kit can be called a “table”). The Court uses this linguistic observation not as a free-floating policy lever, but as a bridge to apply ordinary meaning in context.
• Statutory text and “starter gun” as a guidepost: Section 921(a)(3)(A) defines “firearm” to include any “weapon (including a starter gun)” that “may readily be converted” to expel a projectile. Congress’s inclusion of starter guns—commercial products that do not fire bullets as sold—signals that “weapon” in this statute includes some unfinished items and that “readily converted” tolerates modest time and effort with common tools. The Polymer80 “Buy Build Shoot” kit, assembled in 21 minutes by a novice, meets or betters that benchmark.
• Consistent usage and §923(i): Section 923(i) requires serialization of a firearm’s “frame or receiver,” even for items that may lack a traditional frame (e.g., silencers) or contain incomplete frames. ATF’s longstanding practice treats a silencer’s outer tube as its “frame or receiver,” and §923(i) has been administered to reach some incomplete articles when serialization is required. Reading “frame or receiver” in §921(a)(3)(B) to include some partially complete items aligns with this internal statutory harmony.

On that footing, the Court rejects categorical rules adopted below. For weapon parts kits, it reasons that some kits (those complete and easily assembled) satisfy both predicates of §921(a)(3)(A): they are “weapons” (in ordinary usage) and “may readily be converted” to fire. For frames or receivers, the Court similarly concludes that items minutes from functionality with common tools can still be “frames” or “receivers” within §921(a)(3)(B). Conversely, the Court acknowledges a boundary: kits or blanks so incomplete or laborious to finish that they cannot fairly be described as “weapons,” “frames,” or “receivers” fall outside the statute. But because the Fifth Circuit adopted across-the-board exclusions, those facial rulings cannot stand.

The Court addresses and rejects several counterarguments:

• “Combination of parts” elsewhere means no kits here: Respondents argued that Congress knew how to regulate “parts” or “combinations of parts” (see §921(a)(4)(C) destructive devices; §921(a)(25) silencers/mufflers) but omitted such phrasing from §921(a)(3)(A), implying exclusion. The Court responds that subsection (A) indeed sweeps more narrowly than those provisions and does not cover standalone parts writ large. But narrower does not mean categorically inapplicable: some kits are “weapons” that are readily converted, and thus are covered without importing “combination of parts” text.
• “Weapon” must include a functional frame/receiver: The majority finds no textual basis for requiring that “weapon” include a fully functional frame or receiver at the moment of sale. Even if it did, some kits might still include a finished frame, undercutting any categorical exclusion.
• Criminal-code anomalies: The dissent worried that including kits within “firearm” would spawn odd results across Chapter 44 (e.g., “unloading” a kit). The Court notes Chapter 44 already treats items like frames and silencers as “firearms” even though some provisions cannot sensibly apply to them. This shows Congress’s definition is capacious; it does not prove kits are excluded.
• NFA spillover and AR-15s: The majority accepts the government’s representation that AR-15 receivers are not machinegun receivers and emphasizes the different texts and purposes of the NFA and GCA. Its GCA analysis does not authorize reclassifying AR-15 receivers as machinegun receivers.
• Lenity and avoidance: Because the case turns on clear statutory text and context with obvious applications, neither doctrine applies in this facial posture.

Impact and Practical Consequences

• Ghost gun regulation: ATF retains authority to require licensing, serialization, recordkeeping, and background checks for makers and sellers of weapon parts kits and unfinished frames or receivers that meet the statute’s “weapon” and “readily convertible” thresholds. Products closely resembling the Court’s examples sit squarely within the GCA.
• Narrow decision; future as-applied litigation: Because the Court decided only a facial challenge, line-drawing remains for future cases. Expect disputes over how “readily” is measured (time, ease, expertise, equipment, availability of other parts) and what counts as sufficiently “complete” to be a “frame” or “receiver.” The Court flagged, but did not resolve, how much weight ATF may give to jigs, tools, or instructions supplied with—or marketed for—an item.
• Compliance pathways: Justice Sotomayor highlighted manufacturers’ and dealers’ familiarity with the GCA’s longstanding regime and ATF’s classification process, which can reduce uncertainty. She suggested that failing to seek classification in close cases may signal willfulness.
• Mens rea protections: Justice Kavanaugh emphasized statutory mens rea: “willfully” for licensing/recordkeeping/serialization (requiring proof the defendant knew the conduct was unlawful) and “knowingly” for background-check violations (knowledge of facts, not necessarily law). He noted the government’s representation at argument that it would likely decline to charge unwitting background-check violators, mitigating fair-notice concerns, though due process arguments may remain in hard cases.
• Administrative law posture: The Court avoided settling whether a Salerno-style “no set of circumstances” test governs facial APA excess-of-authority challenges. Justice Alito cautioned against silently importing Salerno to APA cases and flagged the broader debate over the scope of “set aside” under §706(2). That debate is left for another day.
• Chevron-free textualism: Citing Loper Bright, the Court adjudicated statutory meaning without deferring to ATF, while treating the agency’s longstanding, consistent practices (not the disputed new steps) as probative evidence of ordinary meaning.
• Public safety and traceability: The outcome preserves the GCA’s core crime-solving and crime-prevention features in the context of rapidly proliferating untraceable firearms, reflecting Congress’s design to regulate not only finished guns but also items quickly made operable.

Complex Concepts Simplified

• Facial vs. as-applied challenges:
  • A facial challenge seeks to invalidate a rule for all applications. The Court proceeded on the parties’ framing that the rule must be set aside only if inconsistent with the statute in all applications.
  • An as-applied challenge contests a rule’s application to particular facts or products. The Court expressly left such disputes for remand or future cases.
• Artifact nouns: Words like “weapon,” “frame,” and “receiver” denote human-made objects. In ordinary usage, such nouns sometimes cover unfinished items whose intended function is clear and easily realized (e.g., a disassembled rifle remains a “weapon”). The Court invoked this linguistic reality to interpret ordinary meaning in context, not to expand the statute beyond its text.
• “Readily convertible”: The statute covers weapons that “may readily be converted” to fire. The Court used a starter gun as a yardstick: if a novice with common tools can convert the item in less than an hour, that is “readily.” The Polymer80 kit met that test at 21 minutes.
• Frames and receivers: A firearm’s “frame” or “receiver” is the core housing for key firing components. Section 921(a)(3)(B) treats a frame or receiver as a firearm, even when sold separately. The Court held that some partially complete items mere minutes from function can be “frames” or “receivers,” especially in light of §923(i)’s serialization requirement and longstanding practice for silencers.
• Rule of lenity and constitutional avoidance:
  • Lenity resolves ambiguity in penal statutes in favor of defendants. The Court found no ambiguity for the core applications at issue.
  • Constitutional avoidance prefers interpretations avoiding serious constitutional questions. The Court saw no such need where text and context were clear for the applications discussed.
• APA “set aside” and facial standard: Section 706(2) empowers courts to set aside agency action “in excess of statutory authority.” Whether a Salerno-like “no set of circumstances” test applies in such facial challenges remains unresolved; the Court assumed the parties’ framing without deciding the standard.

How the Dissents Would Have Resolved the Case

• Justice Thomas (dissenting):
  • Would hold the rule exceeds the GCA. He reads “frame” and “receiver” to mean the basic, already-functional core of a firearm and rejects including objects that must be “converted” to become frames or receivers.
  • Emphasizes structural cues: §921(a)(3)(A) explicitly covers weapons “readily … converted,” but §921(a)(3)(B) omits such language. He would not import the “readily converted” concept into subsection (B).
  • Criticizes reliance on “artifact nouns” and on extrinsic materials (jigs, instructions, marketing) to transform unregulated items into “frames or receivers.”
  • Warns of NFA spillover (e.g., conversion of AR-15 receivers), and argues the rule of lenity should control if ambiguity exists, invoking Thompson/Center’s approach to parts kits and “combination of parts” drafting.
  • Objects to the Court’s facial-challenge approach in the APA context and would not use that framework to uphold a definition that he views as overbroad.
• Justice Alito (dissenting):
  • Agrees the rule covers the Court’s extreme examples but questions whether a Salerno-style facial standard should govern APA cases. He would solicit further briefing or remand for the Fifth Circuit to address the proper standard.
  • Flags the broader administrative law implications, including the unsettled scope of “set aside” under §706(2) and the risk of insulating overbroad rules if Salerno is imported wholesale.

Key Takeaways and Forward-Looking Guidance

• Holding: ATF’s 2022 rule is not facially inconsistent with the GCA insofar as it covers:
  • Weapon parts kits that are “weapons” and “may readily be converted” to fire (e.g., complete kits assembled in minutes with common tools); and
  • Partially complete frames or receivers that can be finished to function in minutes with common tools.
• Non-holding:
  • No categorical approval of the rule’s application to all kits or blanks; raw materials and items far from finished remain outside the GCA.
  • No resolution of whether or how ATF may consider jigs, tools, or instructions in classifying items; that question is open.
  • No decision on whether a Salerno-like test governs facial APA challenges or on the proper scope of vacatur under §706(2).
• Compliance:
  • Entities should assess products against the “starter gun” benchmark and ATF’s “readily” factors (time, ease, expertise, equipment, availability of other parts).
  • Submitting items for ATF classification can reduce risk; failure to do so may bear on “willfulness.”
  • Mens rea matters: “willfully” for licensing/serialization/recordkeeping; “knowingly” for background checks. Government representations suggest cautious charging in borderline background-check cases, but due process arguments may persist.
• Litigation landscape:
  • Expect as-applied challenges over close-call products and disputes over the evidentiary weight of jigs/tools/marketing.
  • Courts will likely refine what counts as “readily convertible” and when an unfinished item is “so far from finished” that it is not a “weapon,” “frame,” or “receiver.”
  • NFA consequences remain cabined by separate text and context; today’s reasoning does not authorize reclassification of AR-15 receivers as machinegun receivers.

Conclusion

Bondi v. Vanderstok stakes out a clear but carefully bounded rule: the GCA’s definition of “firearm” extends to some non‑operable products—namely, weapon parts kits and partially complete frames or receivers that are minutes away from functionality with common tools—because Congress defined “firearm” to include weapons “readily … converted” and the “frame or receiver” of such weapons. The Court grounded its decision in ordinary meaning, internal statutory coherence (particularly the starter-gun reference and §923(i)’s serialization mandate), and the statute’s public-safety purposes, while disclaiming deference and declining to adopt a global facial-challenge test for APA cases.

The decision preserves ATF’s ability to address an exponential rise in untraceable “ghost guns,” while ensuring that truly raw or remote precursors remain beyond the GCA’s reach. It also flags important open questions—how to weigh jigs and instructions, what makes conversion “readily” achievable in close cases, and what standard governs facial APA challenges. As future disputes refine these edges, this opinion’s central contributions—a practical “starter gun” yardstick for readiness and a context-sensitive understanding of artifact nouns within the GCA—will frame the analysis for courts, agencies, and the firearms industry alike.