United States Court of Appeals 

for the Fifth Circuit ____________ 

No. 23-10718 

____________ 

Jennifer VanDerStok; Michael G. Andren; Tactical 

Machining, L.L.C., a limited liability company; Firearms Policy 

Coalition, Incorporated, a nonprofit corporation, 

Plaintiffs—Appellees, 

Blackhawk Manufacturing Group, Incorporated, doing 

business as 80 Percent Arms; Defense Distributed; Second 

Amendment Foundation, Incorporated; Not An L.L.C., 

doing business as JSD Supply; Polymer80, Incorporated, 

Intervenor Plaintiffs—Appellees, 

versus

Merrick Garland, U.S. Attorney General; United States 

Department of Justice; Steven Dettelbach, in his official 

capacity as Director of the Bureau of Alcohol, Tobacco, Firearms and Explosives; 

Bureau of Alcohol, Tobacco, Firearms, and Explosives, 

Defendants—Appellants. 

______________________________ 

Appeal from the United States District Court 

for the Northern District of Texas 

USDC No. 4:22-CV-691 

______________________________ 

Before Willett, Engelhardt, and Oldham, Circuit Judges.

United States Court of Appeals 

Fifth Circuit 

FILED 

November 9, 2023 

Lyle W. Cayce 

Clerk 

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Kurt D. Engelhardt, Circuit Judge: 

 It has long been said—correctly—that the law is the expression of 

legislative will.1

 As such, the best evidence of the legislature’s intent is the 

carefully chosen words placed purposefully into the text of a statute by our 

duly-elected representatives. Critically, then, law-making power—the ability 

to transform policy into real-world obligations—lies solely with the 

legislative branch.2

 Where an executive agency engages in what is, for all 

intents and purposes, “law-making,” the legislature is deprived of its 

primary function under our Constitution, and our citizens are robbed of their 

right to fair representation in government. This is especially true when the 

executive rule-turned-law criminalizes conduct without the say of the people 

who are subject to its penalties. 

The agency rule at issue here flouts clear statutory text and exceeds 

the legislatively-imposed limits on agency authority in the name of public 

policy. Because Congress has neither authorized the expansion of firearm 

regulation nor permitted the criminalization of previously lawful conduct, the 

_____________________ 

1

 “Positive law is a manifestation of the legislative will.” Arnold v. United States, 13 

U.S. 104, 119 (1815); see also Farrar v. United States, 30 U.S. 373, 379 (1831) (“[The 

President] cannot in the absence of law exercise the power of making contracts, and much 

less, as in this case, against the expression of the legislative will.”) (emphasis added); Kindle 

v. Cudd Pressure Control, Inc., 792 F.2d 507, 512 (5th Cir. 1986) (describing “the express 

legislative will” as “the determinant”); Sylvia Dev. Corp. v. Calvert Cnty., Md., 48 F.3d 

810, 820 (4th Cir. 1995) (noting the “deference to legislative will” inherent in statutory 

interpretation); Winstead v. Ed's Live Catfish & Seafood, Inc., 554 So. 2d 1237, 1242 (La. Ct. 

App. 1989), writ denied, 558 So. 2d 570 (La. 1990) (“The supreme expression of legislative 

will . . . is of course the codes and statutes.”); In re Chin A On, 18 F. 506, 506–07 (D. Cal. 

1883) (“[I]t is the duty of the court to obey the law, as being the latest expression of the 

legislative will.”). 

2 See Forrest General Hospital v. Azar, 926 F.3d 221, 228 (5th Cir. 2019) (“The 

Constitution, after all, vests lawmaking power in Congress. How much lawmaking power? 

‘All,’ declares the Constitution’s first substantive word.”). 

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proposed rule constitutes unlawful agency action, in direct contravention of 

the legislature’s will. Accordingly, for the reasons set forth below, we 

AFFIRM IN PART and VACATE AND REMAND IN PART the 

judgment of the district court. 

I. Statutory and Regulatory Background 

In April of 2022, the Bureau of Alcohol, Tobacco, Firearms, and 

Explosives (“ATF”) issued a Final Rule in which the terms “firearm” and 

“frame or receiver,” among others, were given “an updated, more 

comprehensive definition.” Definition of “Frame or Receiver” and 

Identification of Firearms, 87 Fed. Reg. 24652 (Apr. 26, 2022) (the “Final 

Rule”). The Final Rule was almost immediately the subject of litigation 

claiming that ATF had exceeded its statutory authority. It is that Final Rule 

that is before this Court now. 

First, a brief history of the regulatory agency under fire here. ATF

was created in 1972 as an independent bureau of the U.S. Department of the 

Treasury.3

 The Homeland Security Act of 2002 later transferred ATF to the 

U.S. Department of Justice, where it remains active today. See 6 U.S.C. 

§ 531. Upon its creation, ATF obtained jurisdiction to act under earlier 

legislation, including the Gun Control Act of 1968 (“GCA”),4

 which 

_____________________ 

3 ATF History Timeline, Bureau of Alcohol, Tobacco, Firearms and Explosives, 

https://www.atf.gov/our-history/atf-history-timeline. 

4

 The GCA’s predecessor statutes include the National Firearms Act of 1934 and 

the Federal Firearms Act of 1938, both of which involved the taxation and regulation of 

firearms. See National Firearms Act of 1934, ch. 757, Pub. L. 73-474, 48 Stat. 1236; Federal 

Firearms Act of 1938, ch. 850, Pub. L. No. 75-785, 52 Stat. 1250 (1938) (repealed 1968). 

Of particular note, the Supreme Court has stated: “The Nation’s legislators chose 

to place under a registration requirement only a very limited class of firearms, those they 

considered especially dangerous.” Staples v. United States, 511 U.S. 600, 622 (Ginsburg, J., 

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permits the regulation and taxation of certain “firearms.” Under the GCA, 

Congress granted to the Attorney General the power to prescribe rules and 

regulations necessary to carry out the GCA’s provisions. See 18 U.S.C. 

§ 926. The Attorney General thereafter delegated this authority to ATF, to 

“[i]nvestigate, administer, and enforce the laws related to alcohol, tobacco, 

firearms, explosives, and arson, and perform other duties as assigned by the 

Attorney General.” 28 C.F.R. § 0.130. Pursuant to this authority, ATF

proposed the Final Rule as an extension of the GCA’s regulation of firearms. 

The GCA requires all manufacturers and dealers of firearms to have 

a federal firearms license; manufacturers and dealers are thus known as 

“Federal Firearms Licensees” or “FFLs.” When those FFLs sell or 

transfer “firearms,” they must conduct background checks in most cases, 

record the firearm transfer, and serialize the firearm. See 18 U.S.C. §§ 922(t), 

923(a), 923(g)(1)(A), 923(i). 

The primary method by which the GCA ensures that the manufacture 

and sale of firearms are regulated as intended is through the imposition of 

criminal penalties.5

 As one example, the GCA generally prohibits “any 

_____________________ 

concurring) (noting also “the purpose of the mens rea requirement—to shield people 

against punishment for apparently innocent activity”). 

5

 The GCA is found in Title 18 of the United States Code, which bears the label 

“Crimes and Criminal Procedure.” See 18 U.S.C. § 922. 

Interestingly, Congress’s jurisdictional hook whereby it finds authority to regulate 

firearms in the manner described is the requirement that the firearm travelled in interstate 

commerce. See generally id.; 18 U.S.C. § 921(2) (defining “interstate or foreign 

commerce”); see also, e.g., 2.43D Possession of a Firearm by a Convicted Felon, Fifth Circuit 

District Judges Association Pattern Jury Instructions Committee, Pattern Jury 

Instructions, Criminal Cases (2019) (requiring, under element number four of the offense, 

that the Government prove beyond a reasonable doubt “[t]hat the firearm [ammunition] 

possessed traveled in [affected] interstate . . . commerce; that is, before the defendant 

possessed the firearm, it had traveled at some time from one state to another”). While not 

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person” who is not “a licensed importer, licensed manufacturer, or licensed 

dealer” (i.e., an FFL) from “importing, manufacturing, or dealing in 

firearms” and from “ship[ping] or transport[ing] in interstate or foreign 

commerce any firearm to any person.” Id. at § 922(a). As another example, 

the GCA prohibits a large class of persons from not only shipping or 

transporting firearms, but from possessing them at all. Id. at § 922(g). Should 

a person commit these or any of the other unlawful acts found in the twentysix subsections of section 922, section 924 authorizes various penalties, 

including fines, imprisonment, or both. Id. at § 924. 

The bedrock of the GCA and its plethora of requirements and 

restrictions is the word “firearm.” The GCA defines a “firearm” as: “(A) 

any weapon . . . which will or is designed to or may readily be converted to 

expel a projectile by the action of an explosive; (B) the frame or receiver of 

any such weapon; (C) any firearm muffler or firearm silencer; or (D) any 

destructive device.” Id. at § 921(a)(3)(C). As no definition for “frame or 

receiver” is given in the GCA, ATF previously defined a “frame or 

receiver” in 1978 as: “That part of a firearm which provides housing for the 

hammer, bolt or breechblock, and firing mechanism, and which is usually 

threaded at its forward portion to receive the barrel.” Title and Definition 

Changes, 43 Fed. Reg. 13531, 13537 (Mar. 31, 1978). This definition remained 

unchanged for over forty years, until ATF issued the Final Rule in 2022. 

ATF’s 1978 regulatory definition sufficiently captured most firearms 

of the era. Modern firearms, however, have developed such that many 

firearms no longer fall within the definition. In the Final Rule, ATF states 

that “the majority of firearms in the United States” no longer have a clear 

_____________________ 

challenged in this appeal, the interstate-commerce requirement may call into question 

ATF’s jurisdictional authority to promulgate certain provisions of the Final Rule. 

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“frame” or “receiver” that includes all three elements of the prior definition 

(that is, a hammer, bolt or breechblock, and firing mechanism). 87 Fed. Reg. 

at 24655. ATF uses the example of an AR-15,6

 which does not have a single 

housing for the bolt (which is part of the “upper assembly”) and the hammer 

and trigger (which is part of the “lower assembly”). Id. Thus, as several 

district courts have recently recognized, the lower assembly of the AR-15, 

taken alone, is likely not covered by federal regulations. See, e.g., United States 

v. Rowold, 429 F. Supp. 3d 469, 475–76 (N.D. Ohio 2019) (“The language of 

the regulatory definition in § 478.11 lends itself to only one interpretation: 

namely, that under the GCA, the receiver of a firearm must be a single unit 

that holds three, not two, components: 1) the hammer, 2) the bolt or 

breechblock, and 3) the firing mechanism.”). Likewise, weapons such as 

Glock semiautomatic pistols, which use a “striker” rather than a “hammer” 

as a firing mechanism, and the Sig Sauer P320 pistol, which has no one unit 

containing those three parts, seemingly may not be regulated under the prior 

GCA-related definitions. 87 Fed. Reg. at 24655. 

The Final Rule was also concerned with the rise of privately made 

firearms (“PMFs”).7

 These PMFs, also known colloquially as “ghost 

guns,” are often made from readily purchasable “firearm parts kits, 

standalone frame or receiver parts, and easy-to-complete frames or 

receivers.” Id. at 24652. Because the kits and standalone parts were not 

_____________________ 

6

 The Supreme Court has held that, to be banned, a weapon must be “both 

dangerous and unusual,” and thus, “the relative dangerousness of a weapon is irrelevant 

when the weapon belongs to a class of arms commonly used for lawful purposes.” Caetano 

v. Massachusetts, 577 U.S. 411, 418 (2016) (Alito, J., concurring). Of course, for many years 

now, millions of AR-15 rifles have been sold to civilians, who may lawfully possess them. 

7

 The Final Rule defines a PMF 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.” 87 Fed. Reg. at 24735. 

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themselves considered “firearms” under any interpretation of the GCA and 

ATF’s related definitions, manufacturers of such kits are neither subject to 

licensing requirements nor required to conduct background checks on 

purchasers. Id. Further, when made for personal use, PMFs “are not 

required by the GCA to have a serial number placed on the frame or 

receiver.” Id. These facts, ATF contends, make PMFs attractive to criminal 

actors and “pose a challenge to law enforcement’s ability to investigate 

crimes.” Id. at 24658. 

Notably, the PMFs that play a central role in the Final Rule were not 

unknown at the time of the GCA’s—or, for that matter, its predecessors’—

enactment. “Because gunsmithing was a universal need in early America, 

many early Americans who were professionals in other occupations engaged 

in gunsmithing as an additional occupation or hobby.” Joseph G.S. Greenlee, 

The American Tradition of Self-Made Arms, 54 St. Mary’s L.J. 35, 66 

(2023). The tradition of at-home gun-making predates this nation’s 

founding, extends through the revolution, and reaches modern times. See id. 

at 48 (“During the Revolutionary War, when the British attempted to 

prevent the Americans from acquiring firearms and ammunition, the 

Americans needed to build their own arms to survive.”). Considering this 

long tradition, “[t]he federal government has never required a license to 

build a firearm for personal use.” Id. at 80. “In fact, there were no restrictions 

on the manufacture of arms for personal use in America during the 

seventeenth, eighteenth, or nineteenth centuries.” Id. at 78 (emphasis 

added). And in perfect accord with the historic tradition of at-home gunmaking, Congress made it exceedingly clear when enacting the GCA that 

“this title is not intended to discourage or eliminate the private ownership or 

use of firearms by law-abiding citizens for lawful purposes.” Pub. L. 90-618, 

Title I, § 101, 82 Stat. 1213, 1213 (Oct. 22, 1968). ATF’s Final Rule alters 

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this understanding by adding significant requirements for those engaged in 

private gun-making activities. 

In response to the observed changes in modern firearm construction, 

the Final Rule provides (in part) that “[t]he terms ‘frame’ and ‘receiver’ 

shall 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, i.e., to house or provide a structure for the 

primary energized component of a handgun, breech blocking or sealing 

component of a projectile weapon other than a handgun.” 87 Fed. Reg. at 

24739. The Final Rule also supplements the 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 action of 

an explosive.” Id. at 24728.8

 The Final Rule took effect on August 24, 2022. 

Id. at 24652. 

II. Factual and Procedural Background 

On August 11, 2022, the plaintiffs in this case9

 filed a petition for 

review in the Northern District of Texas. The plaintiffs claimed that two 

_____________________ 

8

 Among other things not substantially challenged in this litigation, the Final Rule 

also defined the term “frame” in relation to handguns and the term “receiver” in relation 

to long guns, defined what “variant” means relative to firearms, required that FFLs 

serialize PMFs that they accept into inventory, and required FFLs to maintain records on 

firearms transactions for the entirety of their business operations, replacing a prior twentyyear requirement. Finally, the Final Rule contains a severability clause. See 87 Fed. Reg. at 

24730. 

9

 The plaintiffs and plaintiff-intervenors in this action are two individuals, Jennifer 

VanDerStok and Michael Andren; Tactical Machining, LLC; Firearms Policy Coalition, 

Inc.; BlackHawk Manufacturing Group, Inc. d/b/a 80 Percent Arms; Defense Distributed; 

Second Amendment Foundation, Inc.; Not An LLC d/b/a JSD Supply; and Polymer80, 

Inc. 

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portions of the Final Rule, which redefine “frame or receiver” and 

“firearm,” exceeded ATF’s congressionally mandated authority. The 

plaintiffs requested that the court hold unlawful and set aside the Final Rule,

and that the court preliminarily and permanently enjoin the Government 

from enforcing or implementing the Final Rule. 

Roughly a month later, the district court issued its first of several 

preliminary injunctions. In this first injunction, the district court found that 

ATF’s new definition of “frame or receiver” is facially unlawful because it 

included “firearm parts that are not yet frames or receivers” in contravention 

of Congress’s clear language in the GCA. VanDerStok v. Garland, 625 F. 

Supp. 3d 570, 578–79 (N.D. Tex. 2022), opinion clarified, No. 4:22-CV00691-O, 2022 WL 6081194 (N.D. Tex. Sept. 26, 2022) (emphasis in 

original). The district court also found that weapon parts kits cannot be 

regulated by ATF under the GCA because “Congress’s definition does not 

cover weapon parts, or aggregations of weapon parts, regardless of whether 

the parts may be readily assembled into something that may fire a projectile.” 

Id. at 580 (emphasis in original). Relying on this same logic, the district court 

subsequently expanded the preliminary injunction and extended similar 

injunctions to other plaintiffs. The Government timely appealed each of 

these injunctions.

While those two appeals were pending, the district court granted 

summary judgment to the plaintiffs and vacated the Final Rule in its entirety. 

VanDerStok v. Garland, No. 4:22-CV-00691-O, 2023 WL 4539591 (N.D. 

Tex. June 30, 2023). The logic of the district court’s order closely tracked its 

_____________________ 

The defendants in this action are Merrick Garland, U.S. Attorney General; the 

United States Department of Justice; Steven Dettelbach, in his official capacity as Director 

of ATF; and ATF. These defendants are collectively referred to herein as “the 

Government.” 

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logic at the injunctive stage: the court held that “the Final Rule’s amended 

definition of ‘frame or receiver’ does not accord with the ordinary meaning 

of those terms and is therefore in conflict with the plain statutory language.” 

Id. at *14. ATF “may not,” the court continued, “properly regulate a 

component as a ‘frame or receiver’ even after ATF determines that the 

component in question is not a frame or receiver.” Id. (emphasis in original). 

Additionally, the court held that because “Congress did not regulate firearm 

parts as such, let alone aggregations of parts,” ATF had no authority to 

regulate weapon parts kits. Id. at *17. Holding that vacatur is “the ‘default 

rule’ for agency action otherwise found to be unlawful,” the court vacated 

the Final Rule under 5 U.S.C. § 706(2)(C). Id. at *18. 

The Government promptly filed a notice of appeal, and subsequently 

filed an emergency motion to stay pending appeal. The district court denied 

the request for a stay pending appeal but granted a seven-day administrative 

stay so that the Government might seek emergency relief from this Court. 

The Government did so. 

This Court considered and denied the Government’s emergency 

motion to stay the district court’s judgment as to the two challenged portions 

of the Final Rule but granted a stay as to the non-challenged provisions of the 

rule. VanDerStok v. Garland, No. 23-10718, 2023 WL 4945360 (5th Cir. July 

24, 2023). The Government then requested a full stay from the Supreme 

Court. Without discussion, the Supreme Court stayed the district court’s 

order and judgment “insofar as they vacate the [F]inal [R]ule” pending (1) 

this Court’s decision and (2) either denial of certiorari thereafter or judgment 

issued by the Supreme Court after grant of certiorari. Garland v. Vanderstok, 

No. 23A82, 2023 WL 5023383 (U.S. Aug. 8, 2023). 

This Court held oral argument on September 7, 2023. Shortly 

beforehand, the Government voluntarily dismissed the two appeals relating 

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to the injunctions. Thus, all that remains before this Court now is the appeal 

of the district court’s final judgment vacating the Final Rule in its entirety. 

III. Standard of Review 

“We review a grant of summary judgment de novo, viewing all the 

evidence in the light most favorable to the nonmoving party and drawing all 

reasonable inferences in that party’s favor.” Parm v. Shumate, 513 F.3d 135, 

142 (5th Cir. 2007) (citing Crawford v. Formosa Plastics Corp., 234 F.3d 899, 

902 (5th Cir. 2000)). “The court shall grant summary judgment if the 

movant shows that there is no genuine dispute as to any material fact and the 

movant is entitled to judgment as a matter of law.” Fed. R. Civ. P. 56(a); see 

Celotex Corp. v. Catrett, 477 U.S. 317, 322–23 (1986). 

IV. Analysis 

The plaintiffs challenged two portions of the Final Rule in the 

underlying lawsuit: (1) ATF’s proposed definition of “frame or receiver” 

including incomplete frames and receivers; and (2) ATF’s proposed 

definition of “firearm” including weapon parts kits. We analyze each 

challenged portion of the Final Rule in turn below, before addressing the 

appropriate relief should these specific portions of the Final Rule be held 

unlawful. 

At the outset, we must ensure that we look through the proper lens 

when analyzing ATF’s actions here.10 “It is axiomatic that an administrative 

agency’s power to promulgate legislative regulations is limited to the 

authority delegated by Congress.” Bowen v. Georgetown Univ. Hosp., 488 U.S. 

_____________________ 

10 Notably, the Chevron doctrine has not been invoked on appeal. Even if the 

Government had done so, Chevron would likely not apply for several reasons, including the 

GCA’s unambiguous text and its imposition of criminal penalties. See, e.g., Cargill v. 

Garland, 57 F.4th 447, 464–66, 472–73 (5th Cir. 2023). 

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204, 208 (1988); see also Clean Water Action v. U.S. Env't Prot. Agency, 936 

F.3d 308, 313 n.10 (5th Cir. 2019) (“To be sure, agencies, as mere creatures 

of statute, must point to explicit Congressional authority justifying their 

decisions.”). In the GCA—the source of ATF’s capacity to promulgate the 

Final Rule—Congress delegated authority to ATF through the Attorney 

General to “prescribe only such rules and regulations as are necessary to 

carry out the provisions of this chapter.” 18 U.S.C. § 926(a). Such a grant of 

authority from the legislature to an executive agency is generally policed by 

the Administrative Procedure Act (“APA”), which allows courts to set aside 

agency action found to be, among other things, “in excess of statutory 

jurisdiction, authority, or limitations, or short of statutory right.” 5 U.S.C. 

§ 706(2)(C). Thus, a core inquiry in a case such as this one is whether the 

proposed agency rule is a lawful extension of the statute under which the 

agency purports to act, or whether the agency has indeed exceeded its 

“statutory jurisdiction, authority, or limitations.” See id.

How do we know when an agency has exceeded its statutory 

authority? Simple: the plain language of the statute tells us so. Therefore, 

“[w]e start, as we always do, with the text.” Sackett v. Env't Prot. Agency, 598 

U.S. 651, 671 (2023); see also Nat'l Fed'n of Indep. Bus. v. Sebelius, 567 U.S. 

519, 544 (2012) (“[T]he best evidence of Congress’s intent is the statutory 

text.”). “In statutory interpretation disputes, a court’s proper starting point 

lies in a careful examination of the ordinary meaning and structure of the law 

itself.” Food Mktg. Inst. v. Argus Leader Media, 139 S. Ct. 2356, 2364 (2019). 

Here, we read the words of the GCA “in their context and with a view to 

their place in the overall statutory scheme.” Davis v. Michigan Dep't of 

Treasury, 489 U.S. 803, 809 (1989). Only where the statutory text shows that 

ATF has “clear congressional authorization” to enact a regulation can such 

a regulation withstand judicial scrutiny. See West Virginia v. Env't Prot. 

Agency, 142 S. Ct. 2587, 2614 (2022) (quoting Util. Air Regul. Grp. v. E.P.A., 

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573 U.S. 302, 324 (2014)). As explained below, we hold that ATF lacked 

congressional authorization to promulgate the two challenged portions of the 

Final Rule. 

a. ATF’s proposed definition of “frame or receiver” 

The GCA includes as a “firearm” the “frame or receiver” of a 

weapon. 18 U.S.C. § 921(a)(3)(C). The GCA itself does not define the term 

“frame or receiver.” See id. The Final Rule, however, newly defines the term 

“frame or receiver” to 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.” 87 Fed. Reg. at 24739. 

Because Congress did not define “frame or receiver” in the GCA, the 

ordinary meaning of the words control. See Bouchikhi v. Holder, 676 F.3d 173, 

177 (5th Cir. 2012). Both a “frame” and a “receiver” had set, well-known 

definitions at the time of the enactment of the GCA in 1968. In 1971, 

Webster’s Dictionary defined a “frame” as “the basic unit of a handgun 

which serves as a mounting for the barrel and operating parts of the arm” and 

a “receiver” as “the metal frame in which the action of a firearm is fitted and 

which the breech end of the barrel is attached.” Webster’s Third International 

Dictionary 902, 1894 (1971). Similarly, ATF’s 1978 definition of frame and 

receiver—the most recent iteration of the definition before the Final Rule’s 

proposed change—defined “frame or receiver” as “[t]hat part of a firearm 

which provides housing for the hammer, bolt or breechblock, and firing 

mechanism, and which is usually threaded at its forward position to receive 

the barrel.”11 43 Fed. Reg. at 13537. As is apparent from a comparison of the 

_____________________ 

11 ATF’s 1968 definition of “frame or receiver” was identical: “That part of a 

firearm which provides housing for the hammer, bolt or breechblock, and firing mechanism, 

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dictionary definitions and the regulatory definition, ATF’s previous 

understanding of “frame or receiver” closely tracked the public’s common 

understanding of such terms at the time of enactment.12

After almost fifty years of uniform regulation, ATF, via the Final 

Rule, now purports to expand the terms “frame” and “receiver,” as they 

were understood in 1968, to include changes in firearms in modern times. But 

the meanings of statutes do not change with the times. See Bostock v. Clayton 

County, 140 S. Ct. 1731, 1738 (2020). “This Court normally interprets a 

statute in accord with the ordinary public meaning of its terms at the time of 

its enactment. After all, only the words on the page constitute the law adopted 

by Congress and approved by the President.” Id. (emphasis added). ATF’s 

inclusion now of “partially complete, disassembled, or nonfunctional” 

frames and receivers materially deviates from past definitions of these words 

to encompass items that were not originally understood to fall within the 

ambit of the GCA. See New Prime Inc. v. Oliveira, 139 S. Ct. 532, 539 (2019) 

(“[W]ords generally should be interpreted as taking their ordinary meaning 

at the time Congress enacted the statute” because “if judges could freely 

invest old statutory terms with new meanings, we would risk amending 

legislation outside the single, finely wrought and exhaustively considered, 

procedure the Constitution commands.”) (cleaned up). As such, the 

proposed definition is an impermissible extension of the statutory text 

approved by Congress. 

_____________________ 

and which is usually threaded at its forward portion to receive the barrel.” Commerce in 

Firearms and Ammunition, 33 Fed. Reg. 18,555, 18,558 (Dec. 14, 1968). 

12 The Government itself acknowledged that “ATF’s prior regulatory definitions 

have been ‘consistent with common and technical dictionary definitions.’” VanDerStok, 

2023 WL 4539591, at *13 (quoting Defs.’ Supp. Br.) (emphasis removed). 

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A plain reading of the Final Rule demonstrates ATF’s error. In the 

GCA’s definition of “firearm,” the first subsection includes flexible 

language such as “designed to or may readily be converted to expel a 

projectile by the action of an explosive.” See 18 U.S.C. § 921(a)(3)(A). But 

the subsection immediately thereafter, which contains the term “frame or 

receiver,” does not include such flexibility. “[W]hen Congress includes 

particular language in one section of a statute but omits it in another section 

of the same Act, it is generally presumed that Congress acts intentionally and 

purposely in the disparate inclusion or exclusion.” Collins v. Yellen, 141 S. Ct. 

1761, 1782 (2021) (citation omitted). ATF’s assertion that Congress has 

repeatedly used language such as “designed to” and “readily” in other 

definitions or statutes only emphasizes the point: Congress explicitly 

declined to use such language in regard to frames or receivers. Thus, we 

presume the exclusion of the phrase “designed to or may readily be 

converted” in the “frame or receiver” subsection to be purposeful, such that 

ATF cannot add such language where Congress did not intend it to exist. See 

Connecticut Nat. Bank v. Germain, 503 U.S. 249, 253–54 (1992) (“We have 

stated time and again that courts must presume that a legislature says in a 

statute what it means and means in a statute what it says there.”). 

There is also a clear logical flaw in ATF’s proposal. As written, the 

Final Rule states that the phrase “frame or receiver” includes things that are 

admittedly not yet frames or receivers but that can easily become frames or 

receivers—in other words: parts. As the district court put it, under the Final 

Rule, “ATF may properly regulate a component as a ‘frame or receiver’ 

even after ATF determines that the component in question is not a frame or 

receiver.” VanDerStok, 2023 WL 4539591, at *14 (emphasis in original). 

Such a proposition defies logic: “a part cannot be both not yet a receiver and 

a receiver at the same time.” Id. (emphasis in original). This confusion 

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highlights ATF’s attempt to stretch the GCA’s language to fit modern 

understandings of firearms without the support of statutory text.13

The Government argues that ATF has historically regulated parts 

that are not yet frames or receivers as frames or receivers, thus making the 

Final Rule a valid extension of past agency practice. This argument fails for 

two reasons. First, as the district court aptly stated, “historical practice does 

not dictate the interpretation of unambiguous statutory terms.” VanDerStok, 

2023 WL 4539591, at *15. Simply because ATF may have acted outside of its 

clear statutory limits in the past does not mandate a decision in its favor 

today. Second, the Government’s current argument regarding the “readily 

converted” language as it applies to frames and receivers is at odds with its 

recent arguments in other courts. For example, in its briefing for a case in the 

Southern District of New York in early 2021, the Government stated that 

“the ‘designed to’ and ‘readily converted’ language are only present in the 

first clause of the statutory definition. Therefore, an unfinished frame or 

receiver does not meet the statutory definition of a ‘firearm’ simply because 

it is ‘designed to’ or ‘can readily be converted into’ a frame or receiver.” 

Fed. Defs.’ Mem. of Law in Support of Mot. for Summ. J., Doc. 98 at 4, 

Syracuse v. ATF, No. 1:20-cv-06885 (S.D.N.Y. Jan. 29, 2021). Clearly, the 

Government has arbitrarily reversed course since authoring the Syracuse

brief, yet it offers no explanation for its new regulatory position. See Acadian 

Gas Pipeline Sys. v. FERC, 878 F.2d 865, 868 (5th Cir. 1989) (“[A]ny 

_____________________ 

13 Perhaps noticing the error in its incredibly broad and murky proposal, ATF

affirmatively excluded from the definition’s scope “a forging, casting, printing, extrusion, 

unmachined body, or similar article that has not yet reached a stage of manufacture where 

it is clearly identifiable as an unfinished component part of a weapon (e.g., unformed block 

of metal, liquid polymer, or other raw material.).” 87 Fed. Reg. at 24739. ATF’s attempt 

to carve out this vague laundry list of unfinished products further demonstrates that the 

proposed definition lacks any objective hook in the statute. 

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departure from past interpretations of the same regulation must be 

adequately explained and justified.”). The sharp change in the 

Government’s argument over a few short years emphasizes the harm in 

relying so heavily on an agency’s historical practice, rather than the 

unambiguous text of the statute. 

Because it clearly conflicts with the plain language of the GCA, the 

challenged portion of the Final Rule that redefines “frame or receiver” to 

include partially complete, disassembled, or nonfunctional frames or 

receivers constitutes unlawful agency action. 

b. ATF’s proposed definition of “firearm” 

The Final Rule purports to supplement the GCA’s definition of 

“firearm” by including the following language: “The term shall 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.” 87 Fed. Reg. at 24728. In other words, ATF expanded the scope 

of the GCA from the explicit “firearm” to now include aggregations of 

weapon parts that can be “readily” assembled into a functional weapon. See 

id.

The district court correctly held that ATF has no authority 

whatsoever to regulate parts that might be incorporated into a “firearm” 

simply because Congress explicitly removed such authority when it enacted 

the GCA. The GCA’s predecessor statute, the Federal Firearms Act 

(“FFA”), had specific language that authorized regulation of “any part or 

parts of” a firearm. See Federal Firearms Act of 1938, Ch. 850, Pub. L. No. 

75-785, 52 Stat. 1250, 1250 (1938) (repealed 1968). However, Congress 

removed this language when it enacted the GCA, replacing “any part or 

parts” with just “the frame or receiver of any such weapon.” Thus, the 

GCA does not allow for regulation of all weapon parts; rather, it limits 

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regulation to two specific types of weapon parts.14 The Final Rule ignores this 

change completely and improperly rewrites and expands the GCA where 

Congress clearly limited it. See Intel Corp. Inv. Pol'y Comm. v. Sulyma, 140 S. 

Ct. 768, 779 (2020) (“When Congress acts to amend a statute, we presume 

it intends its amendment to have real and substantial effect.”) (citation 

omitted). Again, the legislative will has been expressed, and we are bound to 

follow it. 

Further, Congress has shown that it knows how to regulate “parts” 

of weapons when it so chooses. For example, section 921(a)(4)(C) of the 

GCA, in defining a “destructive device” (one of the four subsections of the 

“firearm” definition), states that such term means “any combination of parts 

either designed or intended for use in converting any device into any 

destructive device.” 18 U.S.C. § 921(a)(4)(C). Congress thus clearly 

regulated combinations or aggregations of “parts” in one section of the 

GCA, yet it did not do so when it defined “firearm” within the same 

statute.15 Another helpful example is the definition of “machinegun” in 26 

_____________________ 

14 In the Senate Report connected to the passage of the GCA, the committee stated 

in reference to the amended definition of “firearm” in section 921(a)(3): “It has been found 

that it is impractical to have controls over each small part of a firearm. Thus, the revised 

definition substitutes only the major parts of the firearm; that is, frame or receiver for the 

words ‘any part or parts.’” S. Rep. No. 90-1097 (1968), as reprinted in 1968 U.S.C.C.A.N. 

2112, 2200. 

15 Yet another example within the same statute: Congress defined “firearm 

silencer” and “firearm muffler” in section 921(a)(25) to include “any combination of parts, 

designed or redesigned, and intended for us in assembling or fabricating a firearm silencer 

or firearm muffler.” 18 U.S.C. § 921(a)(25) (emphasis added). 

And another example: In section 921, Congress defined “handgun” to include 

“any combination of parts from which a firearm described in subparagraph (A) can be 

assembled.” 18 U.S.C. § 921(a)(30)(B) (emphasis added). 

And another: In section 922, when defining certain unlawful acts under the GCA, 

Congress explicitly stated that “[i]t shall be unlawful for any person to assemble from 

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U.S.C. § 5845(b), which includes “any part . . . or combination of parts 

designed and intended, for use in converting a weapon into a machinegun, 

and any combination of parts from which a machinegun can be assembled.” 

Conversely, in defining “firearm” under the GCA, Congress used more 

constrained language aimed at specifically named weapon parts, not any and 

all combinations of weapon parts that could later be assembled into a 

functioning weapon. In sum, the word “parts” is conspicuously absent from 

the definition of “firearm” in section 921, despite Congress’s consistent—

and meticulous—use of the word in other statutory provisions. See Buckeye 

Check Cashing, Inc. v. Cardegna, 546 U.S. 440, 448 n.3 (2006) (“Our more 

natural reading is confirmed by the use of the word . . . elsewhere in the 

United States Code.”). The point is a simple one: If Congress wanted to 

regulate aggregations of weapon parts with respect to “firearms,” it could 

have. Congress, however, chose not to do so,16 and ATF may not alter that 

decision on its own initiative. ATF cannot legislate. 

_____________________ 

imported parts any semiautomatic rifle or any shotgun.” 18 U.S.C. § 922(r) (emphasis 

added). 

Moreover, to further demonstrate the particular use by Congress of the term 

“parts” and the assembling of parts: The 1990 Crime Control Bill, H.R. 5269, would have 

made it unlawful to assemble a semi-automatic rifle or shotgun that is identical to one that 

could not be imported. See Crime Control Act, § 2204, P.L. 101-647 (1990), enacting 

current 18 U.S.C. § 922(r). Congresswoman Jolene Unsoeld (D., Wash.) offered an 

amendment to kill the ban on domestic manufacturing by inserting “from imported parts” 

into the bill such that the enactment, as passed, made it unlawful “to assemble from 

imported parts any semi-automatic rifle or any shotgun which is identical to any rifle or 

shotgun prohibited from importation . . .” She argued—correctly—that “Congress, not a 

nameless, faceless bureaucrat in the Treasury Department, should decide which firearms 

Americans can own.” 136 Cong. Rec. H8863–64 (Oct. 4, 1990). The Unsoeld amendment 

passed by a vote of 257 to 172. See id. at H8867; 18 U.S.C. § 922(r). 

16 The Government apparently recognized as much in recent litigation, arguing that 

“Congress has chosen to exclude firearm parts from the scope of the GCA, including parts 

that could be assembled with a homemade receiver and frame to make a firearm.” Gov’t’s 

Mot. to Dismiss, California v. ATF, No. 3:20-cv-06761, 2020 WL 9849685 (N.D. Cal. Nov. 

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ATF finds its primary justification for regulating weapon parts kits in 

the “designed to or may readily be converted to” language in the GCA’s 

definition of “firearm.” The Government argues that the statute captures 

any item or items that may be transformed or changed into a working firearm, 

based on the dictionary definition of “convert”17 at the time of the GCA’s 

enactment. Because weapon parts kits allow individuals to “convert” various 

parts into an operational firearm, the Government argues, the Final Rule’s 

proposed definition falls clearly within the GCA’s ambit. 

But this stretches the words too far. The Government wants the word 

“convert” to be all-encompassing, such that any process or procedure that 

could ultimately lead to a finalized firearm can be regulated under the GCA’s 

language. The language, however, is much more precise than that. In fact, 

the Government’s emphasis on the word “convert” ignores the surrounding 

words: the GCA does not just regulate anything that can be “converted” (or, 

to use the Government’s proposed synonym, “transformed”) into a firearm 

but rather regulates “any weapon” that “may readily be converted” into a 

functional firearm. The phrase “may readily be converted”18 cannot be read 

_____________________ 

30, 2020). Notably, the Government went on to assert that “Congress has also chosen to 

permit the home manufacture of unserialized firearms for personal use.” Id. Much like in 

the Syracuse brief, supra, the Government seemingly took a completely opposite position in 

previous litigation than it takes before this Court in the present matter. 

17 The Government cites to Webster’s 1968 edition to define “convert” as “to 

change from one state to another; alter in form, substance, or quality; transform, 

transmute.” Webster’s Third New International Dictionary of the English Language 499 

(1968) (formatting altered). 

18 Further demonstrating its misunderstanding and misuse of the statutory text, 

ATF apparently equates the phrase “readily be converted” from the GCA with the phrase 

“be readily restored” in the National Firearms Act (“NFA”). However, these two 

different statutes have radically different regulatory scopes: the former regulates ordinary 

firearms (like a standard-issue pistol or rifle), while the latter regulates machine guns, 

suppressors, and short-barreled shotguns that are among the most heavily controlled items 

in our country (if not the world). It is unsurprising that, given their very different scopes, 

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to include any objects that could, if manufacture is completed, become 

functional at some ill-defined point in the future. This would strip the word 

“readily”19 of its meaning, revert the GCA to its prior articulation in the 

FFA, and allow for regulation of weapon parts generally, which, as we have 

seen, was not Congress’s intent in passing the GCA. Look no further than 

the words ATF used in the Final Rule’s proposed “firearm” definition: it 

includes weapon parts kits that “may readily be completed, assembled, 

restored, or otherwise converted to expel a projectile.” 87 Fed. Reg. at 

24728. Reading “converted” in conjunction with the other listed verbs—

“completed, assembled, restored”—we can see that the definition itself 

contemplates less drastic measures than the full transformation actually 

_____________________ 

courts have interpreted these texts to reach very different results. Compare United States v. 

16,179 Molso Italian .22 Caliber Winlee Derringer Convertible Starter Guns, 443 F.2d 463, 

465 (2d Cir. 1971) (interpreting the GCA’s “readily be converted” text to mean something 

as short as twelve minutes), with United States v. Smith, 477 F.2d 399, 400–01 (8th Cir. 

1973) (interpreting the NFA’s “be readily restored” text to mean up to eight hours of 

work, done in a professional shop, by an individual with an advanced understanding of 

metallurgy). Despite these differences, in the Final Rule, ATF expressly conflates the two 

statutory phrases and claims that it can regulate partially complete “frames or receivers” 

using either standard. See, e.g., 87 Fed. Reg. at 24661 n.43 (relying on Winlee Derringer and 

Smith); id. at 24678–79 (relying on NFA and GCA interchangeably). This haphazard 

combination of standards employed by ATF in its Final Rule is the direct result of an 

agency that has strayed too far from its statutory foundation provided by Congress. 

19 ATF itself understood the importance of the word “readily” in the statute—the 

Final Rule includes numerous factors that might help ATF determine when something can 

“readily” be made into a working firearm. 87 Fed. Reg. at 24735. The appellees make many 

well-reasoned arguments regarding the ambiguity and vagueness of the Final Rule’s 

“readily” standard. To the extent ATF relies on such a subjective multi-factor test to 

determine on a case-by-case basis when parts may “readily” be converted into a working 

firearm, this Court looks to the wisdom of the Supreme Court: “It is one thing to expect 

regulated parties to conform their conduct to an agency’s interpretations once the agency 

announces them; it is quite another to require regulated parties to divine the agency’s 

interpretations in advance or else be held liable . . .” Christopher v. SmithKline Beecham 

Corp., 567 U.S. 142, 158–59 (2012). 

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required by these parts kits. See Hilton v. Sw. Bell Tel. Co., 936 F.2d 823, 828 

(5th Cir. 1991) (“When general words follow an enumeration of . . . things, 

such general words are not to be construed in their widest extent, but are to 

be held as applying only to . . . things of the same general kind or class as those 

specifically mentioned.”). The Government’s attempt to use the word 

“convert” to justify its unprecedented expansion of the GCA thus collapses 

upon a cursory reading of the text. 

The Government responds that courts have long recognized that 

disassembled, or nonoperational, weapons constitute “firearms” under the 

GCA, and cites our decision in United States v. Ryles, 988 F.2d 13, 16 (5th 

Cir. 1993). There, a defendant was in possession of a “disassembled [firearm] 

in that the barrel was removed from the stock and that it could have been 

assembled in thirty seconds or less.” Id. We held that because this 

“disassembled shotgun could have been ‘readily converted’ to an operable 

firearm,” it constituted a firearm under the GCA. Id. Unlike the firearm in 

Ryles, weapon parts kits are far from being “operable.” Assembling a weapon 

parts kit takes much longer than thirty seconds, and the process involves 

many additional steps. Because of these differences, weapon parts kits are not 

“‘readily converted’ to an operable firearm,” and thus they do not constitute 

“firearms” under the GCA. Id.

Consider the long-standing tradition of at-home weapon-making in 

this country. See Greenlee, supra. We assume Congress was familiar with the 

relevant historical context when writing the GCA, yet Congress made no 

clear reference to aggregations of weapon parts or PMFs generally in the text 

of the GCA. Rather, as noted above, Congress clearly stated that the GCA

“is not intended to discourage or eliminate the private ownership or use of 

firearms by law-abiding citizens for lawful purposes.” 82 Stat. at 1213. 

Congress also emphasized that “it is not the purpose of [the GCA] to place 

any undue or unnecessary Federal restrictions or burdens on law-abiding 

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citizens with respect to the acquisition, possession, or use of firearms 

appropriate to the purpose of hunting, trapshooting, target shooting, 

personal protection, or any other lawful activity.” Id. at 1213–14. ATF’s 

Final Rule, however, places substantial limits on the well-known and 

previously unregulated right to “the private ownership or use of firearms by 

law-abiding citizens for lawful purposes.” Id. at 1213. 

Take, for example, an individual who buys a weapon parts kit 

containing several unfinished parts he later intends to build and adapt into a 

functional firearm for his personal use. Section 922 of the GCA, which uses 

the term “firearm” to describe many of the “unlawful acts” contained 

therein, may place additional burdens on this individual now that ATF has 

included aggregations of parts in the definition of “firearm.” Parts contained 

in the kit, which were previously unregulated, could now fall into the Final 

Rule’s new definitions, such that the individual cannot sell,20 transport to 

another state,21 or, in some instances, possess the parts at all.22 And key 

determinations, like which parts are regulated, what stage of manufacture 

they must be in, and how many together constitute an actual “firearm,” are 

exceedingly unclear under the Final Rule, such that the individual must guess 

at what he is and is not allowed to do.23 By expanding the types of items that 

are considered “firearms,” ATF has cast a wider net than Congress 

_____________________ 

20 18 U.S.C. § 922(a)(1). 

21 Id. at § 922(a)(2). 

22 Id. a § 922(g). 

23 See United States v. Nat'l Dairy Corp., 372 U.S. 29, 32–33 (1963) (“[C]riminal 

responsibility should not attach where one could not reasonably understand that his 

contemplated conduct is proscribed.”); Johnson v. United States, 576 U.S. 591, 595 (2015) 

(“Government violates [the due process clause] by taking away someone’s life, liberty, or 

property under a criminal law so vague that it fails to give ordinary people fair notice of the 

conduct it punishes, or so standardless that it invites arbitrary enforcement.”). 

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intended: under the Final Rule, the GCA will catch individuals who 

manufacture or possess not just functional weapons, but even minute weapon 

parts that might later be manufactured into functional weapons. The Final 

Rule purports to criminalize such conduct and impose fines, imprisonment, 

and social stigma on persons who, until the Final Rule’s promulgation, were 

law-abiding citizens. ATF cannot so transform the GCA to include aspects 

of the nation’s firearm industry that were previously—and purposefully—

excluded from the statute.24

As the district court succinctly stated, “the Gun Control Act’s precise 

wording demands precise application.” VanDerStok, 2023 WL 4539591, at 

*17. Yet ATF’s proposed definition is not only imprecise, ambiguous, and 

violative of the statutory text, it also legislates. Thus, the challenged portion 

of the Final Rule that redefines “firearm” to include weapon parts kits 

constitutes unlawful agency action. 

c. Public policy concerns 

The Government and amici argue that the challenged portions of the 

Final Rule must be upheld to promote important public policy interests and 

carry out the essential purpose of the GCA. They point to serious concerns 

regarding public safety, the apparent rise in criminal usage of “ghost guns,” 

and the current difficulties in firearm tracing for law enforcement. Without 

the Final Rule, they argue, bad actors will use the “substantial loopholes” in 

_____________________ 

24 Congress has been particular in limiting ATF’s authority in a number of 

respects. In fact, when the NFA was reenacted as Title 2 of the GCA, and remained a 

chapter of the Internal Revenue Code, it set forth definitions including “machine gun” and 

“rifle,” as well as for particular parts. It also excluded from the definition of “firearm” 

certain weapons. Thereafter, ATF began removing excepted weapons from this category, 

thus bringing them within the NFA’s definition of prohibited weapons. Congress 

responded in kind and acted to prevent ATF from doing so. See Consolidated and Further 

Continuing Appropriations Act, 2012, P.L. 112-55, 125 Stat. 552, 609 (Nov. 18, 2011). 

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the text to completely circumvent the GCA and, ultimately, gut the law 

entirely. 

“However, the fact that later-arising circumstances cause a statute 

not to function as Congress intended does not expand the congressionallymandated, narrow scope of the agency’s power.” Texas v. United States, 497 

F.3d 491, 504 (5th Cir. 2007). Likewise, “an administrative agency’s power 

to regulate in the public interest must always be grounded in a valid grant of 

authority from Congress.” Food & Drug Admin. v. Brown & Williamson 

Tobacco Corp., 529 U.S. 120, 161 (2000). Where the statutory text does not 

support ATF’s proposed alterations, ATF cannot step into Congress’s 

shoes and rewrite its words, regardless of the good intentions that spurred 

ATF to act. 

As this Court stated in Cargill v. Garland, “it is not our job to 

determine our nation’s public policy. That solemn responsibility lies with the 

Congress.” 57 F.4th 447, 472 (5th Cir. 2023). While the policy goals behind 

the Final Rule may be laudable, neither ATF nor this Court may, on its own 

prerogative, carry out such goals. That heavy burden instead falls squarely on 

Congress. See Biden v. Nebraska, 143 S. Ct. 2355, 2372 (2023) (“The question 

here is not whether something should be done; it is who has the authority to 

do it.”). “If judges could add to, remodel, update, or detract from old 

statutory terms . . . we would risk amending statutes outside the legislative 

process reserved for the people’s representatives. And we would deny the 

people the right to continue relying on the original meaning of the law they 

have counted on to settle their rights and obligations.” Bostock, 140 S. Ct. at 

1738. Any “loopholes” in the law must be filled by Congress, not by ATF, 

and not by this Court. See Cargill, 57 F.4th at 461 (“Perhaps Congress’s 

choice of words was prudent, or perhaps it was not. That is not for us to 

decide.”). 

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Our concern for strict adherence to statutory text is especially 

heightened here where the Final Rule purports to criminalize what was 

previously lawful conduct. As described above, section 922 of the GCA

describes a plethora of “unlawful acts” related to firearm possession, use, 

and sale, and section 924 describes the penalties for any violations, including 

hefty fines and imprisonment of up to ten years. See 18 U.S.C. §§ 924, 926. 

Because ATF’s Final Rule expands the scope of the GCA to include 

previously unregulated conduct, an ordinary citizen who owns certain 

firearm-related items (and which items are included is only ATF’s guess) 

may now be subjected to the criminal penalties contained within the GCA

practically overnight, without the input of Congress. While agencies may 

enact regulations under a penal statute that result in criminal liability, the 

agencies must always look to statutory authority to sanction their actions. 

Only Congress can actually criminalize behavior.25 Yet the Final Rule plainly 

exceeds the limits Congress itself placed on criminal liability in the realm of 

firearm regulation.26 We therefore hold unlawful the two challenged portions 

of the Final Rule as improper expansions of ATF’s statutory authority. 

_____________________ 

25 See, e.g., 1 Charles E. Torcia, WHARTON’S CRIMINAL LAW § 10 (15th 

ed. 2019) (“It is for the legislative branch of a state or the federal government to 

determine . . . the kind of conduct which shall constitute a crime.”); but see Brenner M. 

Fissell, When Agencies Make Criminal Law, 10 U.C. Irvine L. Rev. 855 (2020) 

(analyzing the growing trend in “administrative crimes,” or crimes created and defined by 

agencies’ rules). 

26 Even if the Court (and the parties) were wrong in concluding that the statute is 

unambiguous, we would nevertheless reach the same conclusion here because under the 

rule of lenity, we construe ambiguous statutes against imposing criminal liability—

precisely what ATF has done here. The rule of lenity is a “time-honored interpretive 

guideline” used by this Court and others “to construe ambiguous statutes against imposing 

criminal liability.” Cargill, 57 F.4th at 471 (quoting Liparota v. United States, 471 U.S. 419, 

429 (1985)). This interpretive rule mandates that, should the GCA’s text be at all unclear, 

we err on the side of those citizens who now face unforeseen criminal liability under ATF’s 

new definitions. See United States v. Thompson/Ctr. Arms Co., 504 U.S. 505, 518 (1992) 

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d. The remedy 

We turn now to the appropriate remedy. The Government argues that 

the district court’s universal vacatur of the entire Final Rule (i.e., not just the 

two challenged portions) was overbroad, regardless of the merits of the case. 

While this Court’s precedent generally sanctions vacatur under the APA,

27

we VACATE the district court’s vacatur order and REMAND to the 

district court for further consideration of the remedy, considering this 

Court’s holding on the merits. 

V. Conclusion 

ATF, in promulgating its Final Rule, attempted to take on the mantle 

of Congress to “do something” with respect to gun control.28 But it is not 

the province of an executive agency to write laws for our nation. That vital 

_____________________ 

(“Making a firearm without approval may be subject to criminal sanction, as is possession 

of an unregistered firearm and failure to pay the tax on one,” and therefore, it is 

“proper . . . to apply the rule of lenity and resolve the ambiguity in [the citizens’] favor.”); 

Crandon v. United States, 494 U.S. 152, 168 (1990) (“[W]e are construing a criminal statute 

and are therefore bound to consider application of the rule of lenity.”). To the extent an 

argument for the statute’s ambiguity holds any water, we would rely on the rule of lenity to 

further bolster the conclusion that ATF, a non-legislative government agency, exceeded 

its statutory authority in promulgating the challenged portions of the Final Rule. See 

Cargill, 57 F.4th at 471 (“[A]ssuming the definition . . . is ambiguous, we are bound to apply 

the rule of lenity.”). 

27 Data Mktg. P'ship, LP v. United States Dep't of Lab., 45 F.4th 846 (5th Cir. 2022) 

(“The default rule is that vacatur is the appropriate remedy” for unlawful agency action.); 

Franciscan All., Inc. v. Becerra, 47 F.4th 368, 374–75 (5th Cir. 2022) (“Vacatur is the only 

statutorily prescribed remedy for a successful APA challenge to a regulation.”); accord 

United Steel v. Mine Safety & Health Admin., 925 F.3d 1279, 1287 (D.C. Cir. 2019) (“The 

ordinary practice is to vacate unlawful agency action.”). 

28 As Justice Thurgood Marshall once wisely advised: “History teaches that grave 

threats to liberty often come in times of urgency, when constitutional rights seem too 

extravagant to endure . . . [W]hen we allow fundamental freedoms to be sacrificed in the 

name of real or perceived exigency, we invariably come to regret it.” Skinner v. Ry. Lab. 

Executives' Ass'n, 489 U.S. 602, 635 (1989) (Marshall, J., dissenting). 

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duty, for better or for worse, lies solely with the legislature. Only Congress 

may make the deliberate and reasoned decision to enact new or modified legislation regarding firearms based on the important policy concerns put forth 

by ATF and the various amici here. But unless and until Congress so acts to 

expand or alter the language of the Gun Control Act, ATF must operate 

within the statutory text’s existing limits. The Final Rule impermissibly exceeds those limits, such that ATF has essentially rewritten the law. This it 

cannot do, especially where criminal liability can—and, according to the 

Government’s own assertions, will—be broadly imposed without any Congressional input whatsoever. An agency cannot label conduct lawful one day 

and felonious the next—yet that is exactly what ATF accomplishes through 

its Final Rule. Accordingly, the judgment of the district court is AFFIRMED to the extent it holds unlawful the two challenged portions of the 

Final Rule, and VACATED and REMANDED as to the remedy.

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Andrew S. Oldham, Circuit Judge, concurring: 

I join my esteemed colleagues’ majority opinion without qualification. 

I write only to explore additional problems with the Final Rule promulgated 

by the Bureau of Alcohol, Tobacco, Firearms and Explosives (“ATF”). See 

Definition of “Frame or Receiver” and Identification of Firearms, 87 Fed. 

Reg. 24652 (Apr. 26, 2022) (“Final Rule”). Part I provides additional 

background. Part II discusses ATF’s unlawful conflation of two 

fundamentally different statutory regimes. Part III addresses the weapon 

parts kit provision. And Part IV considers the unfinished frame or receiver 

provision. 

I. 

 ATF’s overarching goal in the Final Rule is to replace a clear, brightline rule with a vague, indeterminate, multi-factor balancing test. ATF’s 

rationale: The new uncertainty will act like a Sword of Damocles hanging 

over the heads of American gun owners. Private gunmaking is steeped in 

history and tradition, dating back to long before the Founding. Millions of 

law-abiding Americans work on gun frames and receivers every year. In those 

pursuits, law-abiding Americans (and the law-abiding gun companies that 

serve them) rely on longstanding regulatory certainty to avoid falling afoul of 

federal gun laws. But if ATF can destroy that certainty, it hopes law-abiding 

Americans will abandon tradition rather than risk the ruinous felony 

prosecutions that come with violating the new, nebulous, impossible-topredict Final Rule. 

Old Rule (a.k.a. 80% Rule) 

Let’s start with the Old Rule. Since 1968, Congress has defined the 

word “firearm” to mean “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 [or] the frame or receiver of any such weapon.” 18 U.S.C. 

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§ 921(a)(3)(A)–(B) (emphasis added). What is a “frame or receiver”? ATF 

defined that by regulation in 1968, too: The “frame or receiver” of a firearm 

is “[t]hat part of a firearm which provides housing for the hammer, bolt or 

breechblock, and firing mechanism, and which is usually threaded at its 

forward portion to receive the barrel.” 33 Fed. Reg. 18,555, 18,558 (Dec. 14, 

1968) (to be codified at 26 C.F.R. pt. 178); see also 43 Fed. Reg. 13,531, 13,537 

(Mar. 31, 1978) (formerly codified at 27 C.F.R. § 478.11 (2020)). That is 

clear: It tells law-abiding gun owners, hobbyists, and gunsmiths when a piece 

of metal stops being a just a piece of metal and starts being the “frame or 

receiver” of a federally regulated firearm subject to federal gun laws and 

felony penalties. 

The Old Rule even came with numerical certainty. In longstanding 

regulatory guidance, ATF took the position that a hunk of metal became a 

federally regulated “frame or receiver” only after it was 80% complete: 

“ATF has long held that items such as receiver blanks, ‘castings’ or 

‘machined bodies’ in which the fire-control cavity area is completely solid 

and un-machined have not reached the ‘stage of manufacture’ which would 

result in the classification of a firearm [under the 1968 Old Rule].” ATF, Are 

80% or “Unfinished” Receivers Illegal?, https://perma.cc/QX2X-8UHQ (last 

reviewed Apr. 6, 2020). The uninitiated might wonder what constitutes an 

unmachined receiver blank or solid fire-control area. So ATF helpfully 

provided pictures. Here are ATF’s Old Rule pictures for an AR-15’s frame 

or receiver: 

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Ibid. (annotations in original). This Old 80% Rule is thus easy to understand, 

predict, and apply: the top two silver receiver pictures are only 80% complete; 

they are thus “unfinished”; and they do not constitute “firearms” under 

federal gun laws. Under the Old 80% Rule, any law-abiding American 

consumer or manufacturer knew that as long as the fire-control area remained 

solid, the silver pieces of metal were just that—metal. They could be bought 

and sold without concern for the federal gun laws.1

 For decades, millions of Americans have lawfully purchased pieces of 

metal like those silver ones and worked on them in garages and workshops 

across the country. Such homemade firearms have a rich history and 

tradition, dating back to the Founding. See, e.g., Joseph G.S. Greenlee, The 

American Tradition of Self-Made Arms, 54 St. Mary’s L.J. 35, 45–71 

(2023). So the Old Rule allowed Americans to purchase the silver pieces of 

metal, to machine the final 20% of the metal in their homes or garages, and 

thus to make 100%-complete receivers. See ROA.228–44 (ATF’s pre-2022 

Old Rule classification letters on partially complete frames and receivers). An 

enthusiast or amateur gunsmith might mill the fire-control area with a drill 

press so the receiver could hold a trigger assembly. And the enthusiast or 

amateur gunsmith might drill three holes through the receiver to hold the 

safety selector, trigger, and hammer pins. And voila: the modern analogue to 

the homemade rifle Daniel Boone’s father gave him when he was 12. 

Greenlee, supra, at 69. 

_____________________ 

1

 Insofar as the Old Rule applied to frames and receivers that were, say, 81% 

complete, ATF regulated pieces of metal that were both (1) frames and receivers and 

(2) things that were not yet frames and receivers. As the majority opinion notes, see ante, at 

15, it is unclear how the GCA permits that. My point in this separate concurrence is that 

even if the GCA permits the Old 80% Rule, it cannot permit ATF’s attempt to regulate any 

piece of metal that has been machined beyond its “primordial” state. E.g., Final Rule, 87 

Fed. Reg. at 24678. 

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New Rule (a.k.a. Final Rule) 

 Congress has done nothing to change the statutory definition of 

“firearm” or “frame or receiver” since 1968.2

 And for 54 years, the 

regulatory text stayed the same too. Then in 2022, without any direction or 

authorization from Congress, ATF changed everything: 

 ATF eliminated the 80% threshold for unfinished “frames or 

receivers.” And it replaced that numerical certainty with “I-know-itwhen-I-see-it” subjectivity that is evocative of Justice Stewart’s 

obscenity standard. See Jacobellis v. Ohio, 378 U.S. 184, 197 (1964) 

(Stewart, J., concurring). Under the New Rule, a hunk of metal turns 

into a federally regulated “frame or receiver” when ATF thinks “it is 

clearly identifiable as an unfinished component part of a weapon.” 

Final Rule, 87 Fed. Reg. at 24728 (emphasis added). 

 ATF promulgated a non-exhaustive list of eight factors that its 

Director may balance in considering whether a hunk of metal 

constitutes a partially complete or disassembled “frame or receiver”: 

“[T]he Director may consider any associated [1] templates, [2] jigs, 

[3] molds, [4] equipment, [5] tools, [6] instructions, [7] guides, or 

[8] marketing materials that are sold, distributed, or possessed with 

[or otherwise made available to the purchaser or recipient of] the item 

or kit.” Id. at 24739. So the silver pieces of metal in the pictures above 

_____________________ 

2

 Indeed, Congress has considered several bills to regulate so-called “ghost guns” 

and rejected them. See, e.g., Untraceable Firearms Act of 2021, S.1558, 117th Cong. (2021). 

No such bill has made it past bicameralism and presentment. Thus, ATF and the Executive 

Branch sought to do through this Final Rule what they could not do through the normal 

legislative process. Cf. Biden v. Nebraska, 143 S. Ct. 2355, 2373 (2023) (“The Secretary’s 

assertion of administrative authority has conveniently enabled him to enact a program that 

Congress has chosen not to enact itself.” (internal quotation and citation omitted)). 

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are now federally controlled firearms, so long as they are sold with a 

jig, template, or other item useful in finishing the receiver. See ibid. 

 ATF promulgated a non-exhaustive list of eight factors that its 

Director may balance in considering whether a hunk of metal can be 

“readily” converted to a “frame or receiver”: “(1) Time, i.e., how 

long it takes to finish the process; (2) Ease, i.e., how difficult it is to do 

so; (3) Expertise, i.e., what knowledge and skills are required; 

(4) Equipment, i.e., what tools are required; (5) Parts availability, i.e., 

whether additional parts are required, and how easily they can be 

obtained; (6) Expense, i.e., how much it costs; (7) Scope, i.e., the 

extent to which the subject of the process must be changed to finish 

it; and (8) Feasibility, i.e., whether the process would damage or 

destroy the subject of the process, or cause it to malfunction.” Id. at 

24735. 

 And ATF changed the statutory definition of firearm to include 

“weapon parts kit[s].” Id. at 24727–28. Such a “kit” consists of gun 

parts. And ATF concedes that none of those parts is a “firearm” under 

federal law. Still, ATF says that a collection of parts is “firearm” if 

ATF, in its wisdom and its subjective judgment, determines the parts 

look like the building blocks of a firearm. Id. at 24689 (weapon parts 

kits are firearms if they are “clearly identifiable” as such). 

Why did ATF promulgate a 98-page Final Rule—replete with 

multiple, non-exhaustive, eight-factor balancing tests and subjective 

standards evocative of Jacobellis—to replace the Old 80% Rule? ATF says its 

concern is so-called “ghost guns”: Frames and receivers finished in private 

homes and garages do not have serial numbers, and that makes it difficult for 

the Government to track the homemade guns. Id. at 24652. (Hence the 

Government’s “ghostly” moniker.) But if that was all ATF cared about, it 

would just require serialization of all frames and receivers—even those (like 

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the silver pieces of metal pictured above) that are only 80% complete. See 27 

C.F.R. § 479.102 (requiring “a manufacturer” to serialize frames and 

receivers). ATF expressly did not do that, however; it instead expressly 

exempted private individuals from serializing their frames and receivers. See

Final Rule, 87 Fed. Reg. at 24653. That is the precise opposite of what ATF 

would do if it cared about tracing so-called “ghost guns.” 

ATF instead chose to change the meaning of “firearm” so that it can 

apply to any piece of metal that has been machined beyond its “primordial” 

state. Why? ATF wants the “flexibility” to regulate unformed, unfinished 

pieces of metal when it, in its judgment, thinks regulation is “necessary.” Id.

at 24669. And ATF wants to “deter” people from relying on “a minimum 

percentage of completeness (e.g., ‘80.1%’).” Id. at 24686. So it deleted the 

Old 80% Rule and replaced it with new, indeterminate, multi-factorbalancing, and eye-of-the-beholder standards. But it never pointed to a single 

homemade gun that escaped regulation under the Old Rule but would stay 

out of criminals’ hands under the New Rule. 

II. 

 ATF’s foundational legal error is that it conflated two very different 

statutes: the Gun Control Act of 1968 and the National Firearms Act of 1934. 

Those two statutes give ATF very different powers to regulate very different 

types of weapons. To take just one very obvious example, when it comes to 

things like machine guns, the National Firearms Act empowers ATF to 

maintain a central registry called “the National Firearms Registration and 

Transfer Record.” 26 U.S.C. § 5841(a). That database requires registration 

of every machine gun; registration of every person who ever possesses it; and 

strict limitations on every machine gun transfer (including a $200 tax on each 

sale and six-to-twelve month waiting periods). None of these restrictions 

apply to transactions involving ordinary firearms under the Gun Control Act. 

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And ATF promulgated the Final Rule under the Gun Control Act to apply to 

all firearms—not just machine guns. Still, ATF mushed the statutes together 

and then liberally borrowed terms from both. 

 I first (A) explain the statutory conflation. Then I (B) explain how 

ATF exploited that conflation to generate its multi-factor balancing tests. 

A. 

First, the statutory conflation. As the majority notes, see ante n.16, 

ATF’s Final Rule repeatedly uses the word “restored”: 

Firearm . . . . The term shall 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. 

. . . 

Partially complete, disassembled, or nonfunctional frame or 

receiver. The terms “frame” and “receiver” shall 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. 

Final Rule, 87 Fed. Reg. at 24735, 24739 (emphasis added). 

 This is unlawful because (1) ATF took the word “restored” from a 

different statute with a very different scope and meaning. And (2) ATF 

cannot defend that choice by pretending that the relevant statute fairly 

includes the word “restored.” 

1. 

First, the two very different gun control statutes. The first is the Gun 

Control Act of 1968, Pub. L. No. 90-618, 82 Stat. 1213 (“GCA”). The GCA 

was Congress’s response to the assassination of President Kennedy. 

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According to the FBI, Lee Harvey Oswald used the pseudonym “A. Hidell” 

to purchase a 6.5x52mm Carcano bolt-action hunting rifle from a mail-order 

advertisement in the back of American Rifleman magazine. Vincent 

Bugliosi, Reclaiming History: The Assassination of John 

F. Kennedy 200 (2007). “A. Hidell” mailed a money order for $21.45 

($19.95 for the rifle and $1.50 for postage) and later picked up the rifle from 

P.O. Box 2915 in Dallas, Texas. Ibid. Congress’s response in the GCA was, 

inter alia, to prohibit mail-order weapons and to impose identification 

requirements that prohibit pseudonymous purchases. See Interstate Shipment 

of Firearms: Hearings on S. 1975 and S. 2345 Before S. Comm. on Com., 88th 

Cong. (1964). The GCA regulates interstate transactions involving any

firearm—including common bolt-action hunting rifles.3

 

By contrast, the National Firearms Act of 1934, Pub. L. No. 73-474, 

48 Stat. 1236 (“NFA”) applies to a much narrower class of firearms and 

firearm accessories—such as fully automatic machine guns.4

 The NFA was 

Congress’s response to gangster shootouts like the St. Valentine’s Day 

Massacre of 1929. On that bloody Valentine’s Day, seven members of Bugs 

Moran’s gang were gunned down in Chicago. The four shooters used at least 

two Thompson submachine guns. Congress’s response in the NFA was, inter 

alia, to impose a 100% tax on machine gun purchases in an effort to reduce or 

_____________________ 

3

 Throughout this opinion, I use “GCA” and “ordinary” to refer to the firearms 

captured in 18 U.S.C. § 921(a)(3)(A)–(B). That includes the types of firearms Americans 

can buy at sporting-goods and big-box stores, like semiautomatic pistols, revolvers, hunting 

rifles, and shotguns. 

4

 Throughout this opinion, I use “NFA items” to refer to the items captured in 26 

U.S.C. § 5845. These include suppressors, id. § 5845(a)(7), and destructive devices, id.

§ 5845(f). Both are NFA items even though they also appear in 18 U.S.C. § 921(a)(3)(C)–

(D). For the sake of simplicity, I use “machine guns” and “NFA items” interchangeably—

both because machine guns are prototypical NFA items and because ATF’s Final Rule 

relies extensively on court precedents involving machine guns. See infra Part II.B.2. 

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eliminate them. See National Firearms Act: Hearings Before the H. Comm. on 

Ways & Means on H.R. 9066, 73d Cong. 12 (1934). That explains why the 

NFA appears in Title 26 (the Internal Revenue Code), as opposed to 

alongside the GCA in Title 18. Today, the NFA applies only to weapons like 

machine guns, short-barreled shotguns and rifles, and suppressors. And it 

imposes numerous restrictions (including transfer taxes and registration 

requirements) that apply only to NFA weapons and not to non-NFA weapons 

like common bolt-action hunting rifles. See, e.g., 26 U.S.C. § 5821 (taxes on 

NFA weapons). 

ATF promulgated the Final Rule under the GCA—not the NFA. See, 

e.g., Notice of Proposed Rulemaking, Definition of “Frame or Receiver” and 

Identification of Firearms, 86 Fed. Reg. 27720, 27726–27 (May 21, 2021) 

(“NPRM”) (citing as statutory basis the terms “firearm,” “frame,” and 

“receiver” in GCA); Final Rule, 87 Fed. Reg. at 24734 (same). That makes 

some sense because ATF wants the Final Rule to apply to every firearm, every 

frame, and every receiver (the GCA’s scope)—not just to NFA items like 

machine guns. 

The problem is that Congress chose to use the word “restored” only

in the NFA and not in the GCA. “That is significant because Congress 

generally acts intentionally when it uses particular language in one section of 

a statute but omits it in another.” Dep’t of Homeland Sec. v. MacLean, 574 

U.S. 383, 391 (2015); see also Russello v. United States, 464 U.S. 16, 23 (1983). 

When Congress defined NFA weapons like machine guns, it chose to reach 

weapons that could be “restored” to be machine guns. See, e.g., 26 U.S.C. 

§ 5845(b) (“The term ‘machinegun’ means any weapon which shoots, is 

designed to shoot, or can be readily restored to shoot, automatically more than 

one shot, without manual reloading, by a single function of the trigger.”) 

(emphasis added). But when Congress defined ordinary GCA “firearms,” it 

chose not to reach weapons that could be “restored” to function as firearms. 

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Rather, the GCA defined “firearm” in relevant part to mean “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.” 18 U.S.C. § 921(a)(3)(A) 

(emphasis added). We must interpret the two statutes to have different 

scopes consistent with their different texts.5

2. 

 At oral argument, ATF’s counsel conceded the agency took the word 

“restored” from the NFA and inserted it into a GCA regulation. See Oral 

Arg. at 0:30–8:00. Counsel defended conflating the two statutes by arguing 

that “restored” (used only in the NFA) is close enough to the text used in 

the GCA (“converted”) that the Government could mush together the two 

statutes and promulgate a Final Rule that uses both terms interchangeably. 

This argument fails for two reasons. First, the ordinary meaning of 

“converted” is not the same as “restored.” To “convert” means to change 

something from one form to a new, different form: “To alter, as a vessel or 

firearm, so as to change from one class or type to another.” Convert, 

Webster’s New International Dictionary 583 (2d ed. 1934; 

1950) (“Webster’s Second”) (emphasis added). To “restore,” by 

contrast, means to bring something back to its original form: “To bring back 

to, or put back into, the former or original state; to repair; to renew; specif. [] 

To rebuild; reconstruct.” Restore, Webster’s Second at 2125. Thus, a 

firearm A can be converted to a new, different B. Or an old, broken firearm A 

_____________________ 

5

 The textual distinction is particularly powerful because Congress knew how to 

use the word “converted” in the NFA when it wanted to. For example, the GCA added 

the definition of “destructive device” to the NFA in 1968. And when it did so, Congress 

used “converted” in the definition of the NFA item “destructive device.” 18 U.S.C. 

§ 921(a)(4)(B). That further underscores the textual anomaly of the word “restored”—

which appears only in the NFA provisions governing things like machine guns, shortbarreled rifles, and short-barreled shotguns. 26 U.S.C. § 5845(b)–(e). 

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can be restored to new, functional A. But it makes no sense to say A is restored

to B, nor does it make sense to say A is converted to A.

6

For example, a semi-automatic rifle like an AR-15 can be “converted” 

to function as a fully automatic machine gun. Such conversions can be 

accomplished by filing away internal parts of a semi-automatic firearm. See 

Staples v. United States, 511 U.S. 600, 603 (1994). Or by replacing them. See 

Roe v. Dettelbach, 59 F.4th 255, 257 (7th Cir. 2023). But either way, the 

firearm is “converted” from one thing (A, a semi-automatic weapon) into a 

different class or type of firearm (B, a fully automatic weapon). And either 

way, the AR-15 is not “restored” into a machine gun because its original state 

(semi-automatic) was not an old version of the renewed one (fully automatic). 

Cf. United States v. TRW Rifle 7.62x51mm Caliber, One Model 14 Serial 

593006, 447 F.3d 686, 691 (9th Cir. 2006) (“The United States argues, and 

we agree, that the ‘former or original state’ of the rifle refers to the essential 

definition of a machinegun, that is whether it was ever capable of firing 

automatically more than one shot, without manual reloading, by a single 

function of the trigger.”). 

Consider another example. If a lifelong Anglican decides to become 

Roman Catholic, a “reasonable person, conversant with the relevant social 

and linguistic conventions” might say that she “converted” from A

(Anglicanism) to B (Catholicism). Cf. John F. Manning, The Absurdity 

Doctrine, 116 Harv. L. Rev. 2387, 2392–93 (2003). But no one would say 

_____________________ 

6

 Note that this critique of “restored” also applies to the Final Rule’s similarly 

inappropriate uses of the words “completed” and “assembled.” See Final Rule, 87 Fed. 

Reg. at 24735, 24739. Neither word appears in the pertinent text of the GCA. See 28 U.S.C. 

§ 921(a)(3). And both words have definitions that diverge from that of the relevant word in 

§ 921(a)(3), “converted.” 

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the lifelong Anglican “restored” her new Catholic faith.7 In faith as in 

firearms, the words “converted” and “restored” are not interchangeable. 

Thus, in the context of ordinary GCA firearms, like bolt-action 

hunting rifles, Congress used the word “converted.” In the context of NFA 

machine guns, Congress used the word “restored.” That means the GCA 

covers firearms (B) and things (A) that can be readily converted into firearms 

(B). Whereas the NFA concerns firearms that start as machine guns (A) and 

can be restored to functioning machine guns (A). 

B.

All of this matters because the central dispute in this case is how far 

back ATF can reach to regulate the A that can be converted to B. Everyone 

agrees ATF can regulate the gun itself, B. But how far back in the 

manufacturing process of the gun B can ATF reach to regulate things A that 

can be theoretically converted into guns? ATF concedes that it cannot reach all 

the way back to “unformed blocks of metal” or metal in its “primoradial 

state.” Final Rule, 87 Fed. Reg. at 24663. So primordial ooze is not A. But 

anything more refined than that is subject to the Final Rule’s multi-factor 

balancing tests and eye-of-the-beholder standards. 

 The GCA, however, says nothing about primordial ooze, unformed 

blocks of metal, or any of ATF’s various indeterminate standards for A. 

Rather, the GCA says ATF can regulate A as a “firearm” only if A can 

_____________________ 

7

 Some may dismiss such “homey examples” on the grounds that ordinary 

meaning is a legal concept without concern for everyday conversation. See, e.g., Tara Leigh 

Grove, Foreword: Testing Textualism’s ‘Ordinary Meaning’, 90 Geo. Wash. L. Rev.

1053, 1082–83 (2022); Tara Leigh Grove, Is Textualism at War with Statutory Precedent?, 

102 Tex. L. Rev. (forthcoming 2024). To the extent that the critique has purchase as a 

theoretical matter, it is irrelevant here. ATF has provided no argument that the analysis of 

ordinary meaning as a legal concept changes the definition of commonplace words like 

“converted” or “restored.” 

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“readily be converted” into a firearm B. 18 U.S.C. § 921(a)(3)(A). That is, a 

firearm is anything (B) that expels a projectile with an explosive, or anything 

(A) that can be readily converted to a thing (B) that fires a projectile with an 

explosive. 

 Consider (1) how courts distinguish “readily be converted” from 

“readily restored.” Then consider (2) how ATF ignores that distinction. 

The result is (3) a fatally vague Final Rule. 

1. 

Let’s start with ordinary GCA firearms. When it comes to ordinary 

firearms, like bolt-action hunting rifles, courts have interpreted “readily be 

converted” to mean minimal effort—something like “three to twelve 

minutes” with a drill and no special skills. See, e.g., United States v. 16,179 

Molso Italian .22 Caliber Winler Derringer Convertible Starter Guns, 443 F.2d 

463, 465 (2d Cir. 1971). The GCA standard arises with some frequency when 

criminal defendants are charged with possessing gun parts or inoperable guns 

that nonetheless count as firearms because they can “readily be converted” 

to fire. See ibid. For example, this disassembled Tec-9 handgun is still a 

“firearm”: 

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United States v. Morales, 280 F. Supp. 2d 262, 277 (S.D.N.Y. 2003). That is 

because it might be reassembled “in about five seconds.” Id. at 272. 

Similarly, an inoperable shotgun can “readily be converted” to GCA firearm 

if it only requires “about fifteen to twenty minutes” of manipulation. United 

States v. Reed, 114 F.3d 1053, 1056 (10th Cir. 1997). And a starter gun—which 

is expressly mentioned in the text of § 921(a)(3)—is a GCA firearm because 

it can be converted to expel projectiles using basic tools, without any 

specialized knowledge, “in a matter of minutes” and “easily [in] less than an 

hour.” United States v. Mullins, 446 F.3d 750, 755–56 (8th Cir. 2006). 

NFA weapons like machine guns are a different story. Recall that 

machine guns face an entirely different and more onerous regulatory 

regime—including registration requirements for every machine gun, 

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registration requirements for every seller and purchaser, $200 taxes for every 

transfer, and multi-month waiting periods. Owing in part to the significantly 

heavier burdens that attach to machine gun ownership, courts have 

interpreted the NFA’s text (“readily restored”) to reach much further than 

the GCA’s text (“readily be converted”). While the GCA only reaches 

conversions that can be accomplished in minutes using minimal effort, the 

NFA reaches restorations that can be accomplished in hours using maximal

effort. 

Take, for example, United States v. Smith, 477 F.2d 399 (8th Cir. 1973) 

(per curiam). That case concerned possession of an unregistered Thompson 

submachine gun. The gun had been permanently decommissioned: Its barrel 

had been filled with metal. Id. at 400. And the gun was welded in two places 

to make it impossible to fire: “The barrel of the gun was welded closed at the 

breech and was also welded to the receiver on the outside under the 

handguard.” Ibid. Nonetheless, the Government proffered an expert to prove 

that a permanently decommissioned weapon could be “readily restored”: 

[The Government’s expert] testified that there are two 

possible ways by which the firearm could be made to function 

as such. The most feasible method would be to cut the barrel 

off, drill a hole in the forward end of the receiver and then 

rethread the hole so that the same or another barrel could be 

inserted. To do so would take about an 8-hour working day in 

a properly equipped machine shop. Another method which 

would be more difficult because of the possibility of bending or 

breaking the barrel would be to drill the weld out of the breech 

of the barrel. 

Ibid. The court held that was sufficient to support Smith’s NFA conviction 

because eight hours in a properly equipped shop with a sophisticated 

understanding of metallurgy constituted a ready restoration. See id. at 400–

01. Other courts have interpreted the NFA to reach a machine gun that was 

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permanently decommissioned by the military “by torch-cutting its 

receiver—the frame portion of the rifle that contains the firing mechanisms, 

located between the barrel and the stock—into two pieces.” TRW Rifle, 447 

F.3d at 688. The court reasoned the machine gun could be “readily restored” 

by welding the two pieces back together and then using “a hand grinder (or 

dremel tool), a splitting disk, a drill press, and hand files” to restore its firing 

mechanism. Id. at 692. The court credited expert testimony that someone 

with the proper tools and knowledge could do that in two hours. Ibid. A 

similar case estimated that the same restoration could be done in six hours. 

See United States v. One TRW, Model M14, 7.62 Caliber Rifle, 441 F.3d 416, 

422–24 (6th Cir. 2006). 

* * * 

 These cases illustrate what should be obvious to any law-abiding 

American: Federal law treats NFA machine guns differently from ordinary 

GCA firearms like bolt-action rifles. 

2. 

The distinction was not obvious to ATF, however. In Footnote 43 of 

the Final Rule, ATF says “readily” means either “readily be converted” 

under the GCA or “readily restored” under the NFA—terms ATF 

understands as interchangeable in a string cite of cases arising under both 

statutes. See Final Rule, 87 Fed. Reg. at 24661 n.43. ATF points to Footnote 

43 and its mishmash of GCA-NFA precedents over and over throughout the 

Final Rule. See id. at 24684 n.96, 24685 n.103, 24698 n.123, 24700 n.125 

(pointing to footnote 43). As ATF explains, “this rule is guided by . . . 

relevant case law.” Id. at 24698. 

The problem is that NFA precedents are not “relevant case law.” 

Ibid. As to ordinary GCA firearms, ATF is limited to regulating things that 

can “readily be converted” into firearms. 18 U.S.C. § 921(a)(3). That means 

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things that are close enough to firearms that they can be finished “in about 

five seconds,” Morales, 280 F. Supp. 2d. at 272, in “about fifteen to twenty 

minutes,” Reed, 114 F.3d at 1056, or in “easily less than an hour,” Mullins, 

446 F.3d at 755. ATF cannot avail itself of the NFA’s much broader for 

machine guns. Yet in interpreting the GCA’s ordinary-gun standard, ATF 

expressly relied on cases like Smith and its eight-hours-in-a-professionalshop-with-expertise standard. See Final Rule, 87 Fed. Reg. at 24662 n.43; see 

also id. at 24678–79 (explicitly linking the Final Rule’s understanding of 

“readily” to the machine-gun-restoration standard under the NFA). 

The practical implications of ATF’s position are staggering. 

According to ATF, the word “readily” means the same thing in the GCA, 

the NFA, and the Final Rule. If that were true, then millions and millions of 

Americans would be felons-in-waiting. That is because the AR-15 is the most 

popular rifle in America; almost 20 million of them were in American homes 

as of 2020. See NSSF Releases Most Recent Firearm Production Figures, 

https://perma.cc/TBS8-JSSH (Nov. 16, 2020). But every single AR-15 can 

be converted to a machine gun using cheap, flimsy pieces of metal—including 

coat hangers. See Mike Searson, Turning Your AR-15 into an M-16, Recoil 

Magazine, https://perma.cc/L5G9-E9BJ (June 5, 2019). That is 

obviously far easier than the 8-hour-in-a-professional-shop standard 

announced in Smith to govern “ready restoration” under the NFA. 

For decades, America’s AR-15 owners have relied on the fact that AR15s are not subject to the NFA’s ready-restoration standard. Recall the NFA 

applies to machine guns B and things that can be “readily restored” to 

function as machine guns B. See supra Part II.A.2. By contrast, an AR-15 was 

never a machine gun B and hence cannot be “readily restored” to a machine 

gun B. Of course, an AR-15 A could be “converted” to a machine gun B. But 

unless that conversion could be done in a few seconds or minutes, see Morales, 

280 F. Supp. 2d. at 272; Reed, 114 F.3d at 1056, AR-15 owners had no reason 

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to worry that their rifles were capable of ready conversion into unregistered 

machine guns. The Final Rule eliminates that certainty, says “readily” 

means the same thing in the GCA and the NFA, and says Americans violate 

federal gun laws if they could in theory manufacture a prohibited weapon in 

eight hours in a professional shop with metallurgical expertise. See Smith, 477 

F.2d at 400; Final Rule, 87 Fed. Reg. at 24661 n.43 (relying on Smith). 

3. 

After conflating the GCA and the NFA, the Final Rule includes a list 

of eight non-exhaustive factors to guide ATF’s understanding of “readily”: 

(1) Time, i.e., how long it takes to finish the process; (2) Ease, 

i.e., how difficult it is to do so; (3) Expertise, i.e., what 

knowledge and skills are required; (4) Equipment, i.e., what 

tools are required; (5) Parts availability, i.e., whether additional 

parts are required, and how easily they can be obtained; 

(6) Expense, i.e., how much it costs; (7) Scope, i.e., the extent 

to which the subject of the process must be changed to finish 

it; and (8) Feasibility, i.e., whether the process would damage 

or destroy the subject of the process, or cause it to malfunction. 

Final Rule, 87 Fed. Reg. at 24735. The Final Rule emphasizes this list is 

“nonexclusive.” Id. at 24698. And ATF explicitly disclaimed the need to 

explain how any of these factors would balance in practice: “It is not the 

purpose of the rule to provide guidance so that persons may structure 

transactions to avoid the requirements of the law.” Id. at 24692. 

This approach violates the Fifth Amendment and its guarantee of fair 

notice. See FCC v. Fox Television Stations, 567 U.S. 239, 253 (2012) (“A 

fundamental principle in our legal system is that laws which regulate persons 

or entities must give fair notice of conduct that is forbidden or required.”). 

The “Government violates this guarantee by taking away someone’s life, 

liberty, or property under a criminal law so vague that it fails to give ordinary 

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people fair notice of the conduct it punishes, or so standardless that it invites 

arbitrary enforcement.” Johnson v. United States, 576 U.S. 591, 595 (2015). 

Even if “some conduct [] clearly falls within the provision’s grasp,” a law 

can still be vulnerable to a vagueness challenge. Id. at 602. With its 

nonexclusive list of eight factors and lack of concrete examples, the Final 

Rule produces “more unpredictability and arbitrariness than the Due Process 

Clause tolerates.” See Sessions v. Dimaya, 138 S. Ct. 1204, 1215 (2018) 

(citation omitted). 

ATF dismisses the problem by pointing to courts that have rejected 

vagueness challenges to the term “readily.” Final Rule, 87 Fed. Reg. at 

24700, n.126 (pointing to cases listed in 87 Fed. Reg. at 24679 n.79). But that 

argument fails for two reasons. Nearly all of ATF’s cited precedents involve 

the NFA, not the GCA. See id. at 24679 n.79 (also citing cases on state laws 

and the ADA). And as discussed above, courts have interpreted the NFA 

more expansively than the GCA. But more relevantly, the cited precedents 

dealt with the word “readily” as it exists in statutory text. They did not 

consider ATF’s nonexclusive eight-factor balancing test with no concrete 

examples. It is the text of the Final Rule, not the text of the statute, which 

falls short of the Due Process Clause.8

ATF also argues that it could provide sufficient guidance in individual 

cases: Where “persons remain uncertain” as to the exact scope of the Rule, 

_____________________ 

8

 ATF essentially responded with variation of the motte-and-bailey argument. See 

Scott Alexander, All in All, Another Brick in the Motte, Slate Star Codex (Nov. 3, 

2014), https://perma.cc/PA2W-FKR9. The Final Rule is clearly more expansive than the 

text of § 921(a)(3). When pressed on due process concerns with the Final Rule, ATF 

retreated to the text of § 921(a)(3) and argued that courts have rejected such attacks on the 

GCA. But the Final Rule is not the GCA. ATF may either have the text of the GCA, as 

upheld against due process challenges by various courts, or the more expansive Final Rule, 

which has never encountered such a challenge. But it may not mix and match legal texts 

with defenses. 

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“they may submit a voluntary request to ATF for a classification.” Final 

Rule, 87 Fed. Reg. at 24692. But this does nothing to cure the Final Rule’s 

vagueness. As important as the Fifth Amendment’s guarantee of fair notice 

to individuals is the Amendment’s prohibition against “arbitrary 

enforcement” by government officials. See Johnson, 576 U.S. at 595 (citing 

Kolender v. Lawson, 461 U.S. 352, 357–358 (1983)). It is thus of no use for 

ATF to say that it will tell ordinary people what they can do. The law exists 

to tell both the people and government officials what they can do. See Sessions, 

138 S. Ct. at 1228 (Gorsuch J., concurring in part and concurring in the 

judgment) (“Vague laws [] threaten to transfer legislative power to police and 

prosecutors, leaving to them the job of shaping a vague statute’s contours 

through their enforcement decisions.”) (citing Grayned v. City of Rockford, 

408 U.S. 104, 108–09 (1972)). The nonexclusive eight-factor balancing test 

provides no guidance to anyone and hence is void for vagueness. 

III. 

 Next consider the Final Rule’s approach to weapon parts kits. The 

Final Rule expands the GCA’s definition of “firearm” to include weapon 

parts kits: 

Firearm . . . . The term shall 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. 

Final Rule, 87 Fed. Reg. at 24735. But this expansion cannot stand for two 

reasons. 

 First, as the majority cogently explains, see ante at 19, Congress knows 

how to regulate gun parts, either individually or as a collection. The GCA’s 

predecessor, the Federal Firearms Act, defined “firearm” to mean “any 

weapon . . . or any part or parts of such weapon.” Pub. L. No. 75-782, 52 Stat. 

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1250, 1250 (1938) (repealed 1968) (emphasis added). But Congress removed 

this language when it enacted the GCA. Moreover, Congress regulates parts 

elsewhere in the GCA (as well as in the NFA). See, e.g., 18 U.S.C. 

§ 921(a)(4)(C) (defining “destructive device” as, inter alia, “any 

combination of parts . . . .”). The omission of any reference to “parts” in 

§ 921(a)(3) indicates that Congress did not sweep “parts” into the GCA’s 

definition of firearm. 

 Second, the structure of § 921(a)(3) presumes that all covered 

firearms have either a frame or a receiver. Therefore, a weapon parts kit that 

does not include a frame or receiver cannot be regulated under § 921(a)(3). 

Start with the statutory text. Section 921(a)(3) defines the term 

“firearm” in four sub-sections: (A), (B), (C), and (D). Consider only (A) and 

(B). Subsection (A) defines “firearm” to include “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.” 18 U.S.C. § 921(a)(3)(A). 

Subsection (B) defines “firearm” to include “the frame of receiver of any 

such weapon.” Id. § 921(a)(3)(B) (emphasis added). With its placement 

immediately following (A), we can easily understand (B)’s “any such 

weapon” language to incorporate the definition of “weapon” in (A). Thus, 

Subsection (B) defines “firearm” to include “the frame of receiver of any 

such 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.” Or 

put another way, § 921(a)(3) defines “firearms” to include, inter alia, certain 

weapons (A) and the frame or receiver of said weapons (B). Section 921(a)(3) 

does not contemplate a weapon covered by (A) that does not have a frame or 

receiver covered by (B). 

Contrast the statute with two hypothetical weapon parts kits covered 

by the Final Rule. The first kit contains a frame as defined by § 921(a)(3)(B). 

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That means that the kit contains a firearm under § 921(a)(3). The frame 

(separate and apart from anything else in the kit) triggers the GCA and its 

various requirements. See, e.g., 18 U.S.C. § 923(i) (“Licensed importers and 

licensed manufacturers shall identify by means of a serial number engraved 

or cast on the receiver or frame of the weapon, in such manner as the 

Attorney General shall by regulations prescribe, each firearm imported or 

manufactured by such importer or manufacturer.”). In this hypothetical, the 

frame is doing all the work—it is sufficient to trigger the GCA, so it does not 

matter what else is included in the frame-containing kit. 

Now consider a different kit covered by the Final Rule: This second 

kit contains no frame or receiver as defined by § 921(a)(3)(B). See Final Rule, 

87 Fed. Reg. at 24685 (“The Department disagrees with the comment that 

weapon parts kits must contain all component parts of the weapon to be 

‘readily’ converted to expel a projectile.”). This kit is incomplete because it 

does not contain a frame or receiver—and hence contains nothing that 

triggers § 921(a)(3)’s text. It beggars belief to suggest that such an incomplete 

parts kit is a weapon in any sense of the word. An incomplete weapon parts 

kit will never turn itself into a functioning weapon of any sort. Any argument 

to the contrary is “[p]ure applesauce.” King v. Burwell, 576 U.S. 473, 507 

(2015) (Scalia, J., dissenting). 

ATF’s only response is to say that it’ll deem incomplete kits as 

“firearms” based on “a case-by-case evaluation of each kit.” Final Rule, 87 

Fed. Reg. at 24685; cf. Jacobellis, 378 U.S. at 197 (Stewart, J., concurring). 

How is any American supposed to know when a collection of gun parts meets 

that standard? 

In sum, § 921(a)(3) contemplates that a covered “weapon” (A) has a 

“frame or receiver” (B). Insofar as the Final Rule seeks to regulate weapons 

that do not, the rule is unlawful. 

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IV.

 Finally, consider the Final Rule’s treatment of unfinished and 

incomplete frames and receivers. This is perhaps ATF’s most aggressive 

attempt to bootstrap hunks of metal and plastic into the GCA’s definition of 

a “firearm.” As explained in the preceding sections of this opinion, the 

GCA’s definition of a “firearm” includes (1) functioning guns, (2) weapons 

that are “designed” to be functioning guns, (3) weapons that can “readily be 

converted” to functioning guns, and (4) the “frame or receiver of any such 

weapon.” 18 U.S.C. § 921(a)(3)(A)–(B). Thus, if a felon possesses a 

functioning handgun, that obviously violates the GCA. If the same felon 

possesses a non-functioning handgun, that still might violate the GCA if the 

gun was “designed” to be a functioning gun. And if the same felon possesses 

a field-stripped handgun,9

 that violates the GCA in two separate ways: the 

gun can be reassembled (and hence “readily be converted” to a functioning 

gun), and the frame or receiver of the field-stripped weapon is a “firearm” 

under § 921(a)(3)(B) even without reassembly. 

But that statutory definition is not capacious enough for ATF. In the 

Final Rule, ATF asserts that anything beyond primordial ooze, liquid 

polymer, and wholly unformed raw metal can constitute a firearm. Here’s 

how ATF explains the bootstrapping: 

(c) Partially complete, disassembled, or nonfunctional frame or 

receiver. The terms “frame” and “receiver” shall include a 

partially complete, disassembled, or nonfunctional frame or 

_____________________ 

9

 Field stripping a firearm involves disassembling it without any special tools for 

routine cleaning and maintenance. See, e.g., Bob Boyd, DIY Guide: Field-Stripping a Glock, 

Shooting Illustrated (Dec. 17, 2019), https://perma.cc/A7CA-YVKC; cf. United 

States v. Spencer, 439 F.3d 905, 911 (8th Cir. 2006) (noting a “field stripped” machine gun 

was disassembled “into approximately ten to fifteen different parts” and “could be 

reassembled in about five or ten minutes”) (quotation omitted). 

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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, i.e., to 

house or provide a structure for the primary energized 

component of a handgun, breech blocking or sealing 

component of a projectile weapon other than a handgun, or 

internal sound reduction component of a firearm muffler or 

firearm silencer, as the case may be. The terms shall not 

include a forging, casting, printing, extrusion, unmachined 

body, or similar article that has not yet reached a stage of 

manufacture where it is clearly identifiable as an unfinished 

component part of a weapon (e.g., unformed block of metal, 

liquid polymer, or other raw material). 

Final Rule, 87 Fed. Reg. at 24739. But this expansion cannot stand, because 

(A) a frame or receiver parts kit is not a frame or receiver, (B) the Final Rule’s 

examples defining “frame or receiver” are nonsensical, and (C) the Final 

Rule fails to sufficiently engage with then-contemporaneous definitions of 

“frame” or “receiver.” 

A.

To begin, a frame or receiver parts kit is not a frame or receiver within 

the meaning of § 921(a)(3)(B). 

Seven years before the GCA was passed, Webster’s Third

defined frame as “the basic unit of a handgun which serves as a mounting for 

the barrel and operating parts of the arm,” Webster’s Third 

International Dictionary 902 (1961), and receiver as “the metal 

frame in which the action of a firearm is fitted and which the breech end of 

the barrel is attached.” Webster’s Third International 

Dictionary 1894 (1961). Now, the Final Rule attempts to expand those 

definitions, so that “frame” includes a “frame parts kit” and “receiver” 

includes a “receiver parts kit.” Final Rule, 87 Fed. Reg. at 24739. 

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But ATF cannot simply add the phrase “parts kit” and regulate as if 

the frame/receiver parts are the frames/receivers themselves. A frame parts 

kit does not serve as “the basic unit of a handgun which serves as a mounting 

for the barrel”; it is a collection of parts that could in theory be assembled 

into a frame. A receiver parts kit is not a “metal frame”; it is a collection of 

parts that can be assembled into a metal frame. Thus, as a matter of commonsense statutory interpretation, the parts kits cannot qualify as frames or 

receivers under § 921(a)(3)(B). See Pensacola Tel. Co. v. W. Union Tel. Co., 96 

U.S. 1, 12 (1877) (presuming that words in statutory text are to be given 

“their natural and ordinary signification.”). 

ATF’s contrary view has no stopping point. For example, ATF says 

it will regulate “[a] complete frame or receiver of a weapon that has been 

disassembled, damaged, split, or cut into pieces, but not destroyed in 

accordance with paragraph (e).” Final Rule, 87 Fed. Reg. at 24739. Paragraph 

(e) in turn states that “[a]cceptable methods of destruction include 

completely melting, crushing, or shredding the frame or receiver.” Ibid. It is 

thus unclear if any gun part could ever fall outside ATF’s definition of a 

“firearm.” On the front end, anything that has been refined beyond 

primordial ooze or raw liquid polymer could one day be a firearm. And on the 

back end, anything that has not been melted down into primordial ooze or 

raw liquid polymer could one day be restored to function as a firearm. 

This makes little sense. If I went to a junk yard and picked up a piece 

of metal that used to be part of a truck, no reasonable person would say I’m 

holding a truck because the metal has been formed beyond primordial ooze 

and hence could be “completed, assembled, restored, or otherwise converted 

to function” as either a truck or truck frame. Likewise, if I cut a truck into 

100 pieces, scattered them on the ground, and then picked up some, no 

reasonable person would say I’m holding a truck or truck frame because the 

piece hadn’t been melted down to its primordial state. 

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B.

 Next, the Final Rule says even unformed pieces of metal or plastic 

can constitute frames and receivers when they are found with instructions or 

jigs. In the section on frames and receivers, the Final Rule gave multiple 

examples of what is or is not a frame or receiver within the meaning of § 

921(a)(3)(B). See Final Rule, 87 Fed. Reg. at 24739. Examples 1 and 4 are key. 

Example 1 provides: 

Frame or receiver: A frame or receiver parts kit containing a partially 

complete or disassembled billet or blank of a frame or receiver that is 

sold, distributed, or possessed with a compatible jig or template is a 

frame or receiver, as a person with online instructions and common 

hand tools may readily complete or assemble the frame or receiver 

parts to function as a frame or receiver. 

Ibid. In contrast, Example 4 provides: 

Not a receiver: A billet or blank of an AR-15 variant receiver without 

critical interior areas having been indexed, machined, or formed that 

is not sold, distributed, or possessed with instructions, jigs, templates, 

equipment, or tools such that it may readily be completed is not a 

receiver. 

Ibid. Note the difference between Example 1 (frame or receiver) and Example 

4 (not a frame or receiver): the presence of a jig or other template. Thus, it is 

the jig or template that triggers the GCA. 

 The implication of these examples is stark. On a workbench you find 

two receiver blanks like the silver ones pictured on page 3 of this opinion. 

Neither has “critical interior areas” that are “indexed, machined, or 

formed.” Ibid. But the right receiver blank is accompanied by a plastic jig. 

The left one is not. Under the Final Rule, the right receiver blank is a frame 

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or receiver, thus triggering a five-year prison sentence for unlicensed 

manufacturing, importing, or dealing. See 18 U.S.C. §§ 922(a)(1)(B), 924 

(a)(1). The left is just innocuous metal. How can this be? It seems that the 

presence of the jig changes that receiver blank from something that is not a 

firearm under § 921(a)(3) to something that is. But § 921(a)(3)(B) only refers 

to frames and receivers. Section 921(a)(3)(B) does not mention jigs (or 

instructions, templates, equipment, tools). How can the jig or template 

change the nature of the receiver blank, such that the blank goes from 

unregulable to regulable under § 921(a)(3)(B)? 

 It obviously cannot. Consider the lumber in every Home Depot across 

America. It obviously has been machined beyond its primordial state; much 

of it has been pressure treated, and all of it has been cut to specified lengths. 

The same is true about every screw, nut, and bolt in the store; all of them 

have been machined beyond their primordial states and cut to specified 

lengths. Now, if I walk into the Home Depot with instructions for making a 

chair, would any reasonable person say I possess a chair? Of course not.10 

C.

 Let’s close with the ATF’s eye-of-the-beholder standard. As noted in 

previous sections of this opinion, dictionaries define frame and receiver—like 

the Old 80% Rule—in terms of critical components, parts, and functions. For 

_____________________ 

10 In its briefing before our court, ATF attempts to engage a related hypothetical 

by arguing that a person possesses a bicycle when they buy a disassembled one. See Blue 

Br. 19. That is a red herring for two reasons. First, a disassembled bicycle is no different 

than a field-stripped gun; the former is a bicycle just as the latter is a gun. See supra note 9 

and accompanying text. Second, the Final Rule reaches far, far beyond a bicycle “shipped 

with plastic guards attached to the gears or brakes that must be removed before it is used.” 

Blue Br. 19. To make the analogue work, ATF would have to contend that metal machined 

beyond its primordial state and rubber machined beyond liquid ooze constitutes a bicycle if 

possessed with a template or instructions for manufacturing the bike. 

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example, the frame or receiver must be able to hold a trigger or the 

breechblock. Or it must have certain parts milled, etc. In the place of these 

standards, ATF said metal or plastic is a frame or receiver if it has “reached 

a stage of manufacture where it is clearly identifiable as an unfinished 

component part of a weapon.” Final Rule, 87 Fed. Reg. at 24739 (emphasis 

added). Or rather, once an ordinary person can look at an object and say that 

it looks like an “unfinished component part of a weapon,” see ibid., it has 

become a frame or receiver within the meaning of § 921(a)(3)(B). How does 

this interact with ATF’s assertions throughout the Final Rule that it now 

regulates anything machined beyond primordial ooze and liquid polymer? 

Unclear. What does “clearly identifiable” mean? Also unclear. What objects 

do ordinary people (who might associate “receivers” more readily with 

football than guns) think are “clearly identifiable” as firearm components? 

Yet again, unclear. All we know is that ATF, like Justice Stewart, is confident 

that it can identify a GCA firearm when it sees one. 

ATF’s problem is that § 921(a)(3)(B) covers objects that are frames 

and receivers, not objects that look like frames or receivers.11 A recent 

Internet fad illustrates the point. Consider the “cakes that look like food” 

Internet trend. See, e.g., Chelsweets, Cakes That Look Like Food: 10 Amazing 

Cakes, YouTube (Jan. 22, 2018), https://perma.cc/UGH6-MXA2. One 

could make a cake that looks like a hamburger, just as one could make a cake 

that looks like a gun frame or receiver. One is “clearly identifiable” as a 

_____________________ 

11 It is no answer to say that the Old 80% Rule allowed the regulated community to 

escape regulation by making 79%-complete frames and receivers. See Final Rule, 87 Fed. 

Reg. at 24686. Such a response might be valid on public policy grounds, but as the majority 

notes above, see ante at 24–26, public policy is the purview of Congress, not the federal 

courts. See Lamie v. U.S. Tr., 540 U.S. 526, 542 (2004) (“If Congress enacted into law 

something different from what it intended, then it should amend the statute to conform it 

to its intent.”). 

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hamburger, just as the other is “clearly identifiable” as a gun part. But that 

does not make the former taste like a Big Mac, just as it does not make the 

latter covered by the GCA. 

* * * 

 The Final Rule is limitless. It purports to regulate any piece of metal 

or plastic that has been machined beyond its primordial state for fear that it 

might one day be turned into a gun, a gun frame, or a gun receiver. And it 

doesn’t stop regulating the metal or plastic until it’s melted back down to 

ooze. The GCA allows none of this. I concur in the majority’s opinion 

holding the Final Rule is unlawful. And I further concur that the matter 

should be remanded to the district court to fashion an appropriate remedy for 

the plaintiffs. 

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