Notice & Comment

Lenity and Agency Deference in Garland v. Cargill, by Tess Saperstein

With the Supreme Court hearing arguments in Garland v. Cargill this term, the Court has been asked to decide the narrow question of whether a bump stock device is a “machinegun” as defined in the National Firearms Act.[1] However, embedded within the case is an issue that raises broad administrative law questions about how the rule of lenity interacts with agencies’ interpretations of statutes with criminal implications. This blog addresses those questions, which I expand upon in my note, High Caliber, Yet Under Fire: The Case for Deference to ATF Rulemaking.[2] In the note, I explore the primary justifications for the rule of lenity, explain why they do not apply when agencies engage in notice-and-comment rulemaking, and argue that, as an agency with technical expertise in an area that experiences rapid technological advancement and is subject to continual political accountability, the ATF presents the prototypical case for agency deference.   


In 2018, following the shooting at a Las Vegas music festival which left 58 people dead, President Donald Trump ordered the Bureau of Alcohol, Tobacco, Firearms, and Explosives (“ATF”) to ban bump stocks, the accessory which helped make the shooting the deadliest in modern American history.  In order to implement the President’s policy decision, the ATF used its rulemaking authority to classify bump stocks as “machineguns,” weapons which were already banned under 18 U.S.C. § 922(o). 

Although the government sought to keep the question presented in Garland v. Cargill as narrow as possible, the respondent may successfully bait the Court into issuing a broader ruling on the rule of lenity and its effect on agency deference. Both parties argue that the statute supports their respective interpretations.[3] However, writing in support of the government’s petition for certiorari, the respondent asked the Court, “to expand the question presented.”[4]  If the Court determined that the definition of “machinegun” is ambiguous, the respondent asked that the Court also address “whether the Fifth Circuit correctly held that the rule of lenity requires courts to construe that statutory ambiguity against the government.”[5] In expanding the question presented, the respondent presents the Court with an opportunity to take a hatchet to agency deference in the interpretation of criminal statutes. 

The National Firearms Act defines “machinegun” as including “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.”[6] In its 2018 final rule, the ATF interpreted “single function of the trigger” to mean “a single pull of the trigger”[7] and “automatically” to mean “as the result of a self-acting or self-regulating mechanism that allows the firing of multiple rounds through a single pull of the trigger,”[8] thereby including bump stocks in the definition of a machine gun.  Since the rule expanded the definition of “machinegun,” individuals who violated the rule by failing to dispose of their bump stocks would be subject to the criminal penalties provided for in the NFA and GCA. In the wave of litigation that followed, bump stock owners challenged the ATF’s interpretation and argued that, given the statutes’ criminal implications, the rule of lenity required that any ambiguity in the NFA and GCA should be resolved in the defendant’s favor. Garland v. Cargill represents one such challenge.   

The Court has wavered as to whether agency interpretations of criminal statutes should be entitled to deference. Just six years after Chevron was decided, Justice Scalia suggested that the rule of lenity may prohibit agency deference in certain situations. In his concurrence in Crandon v. United States, Justice Scalia stated, “we have never thought that the interpretation of those charged with prosecuting criminal statutes is entitled to deference.”[9] Nonetheless, the Court continued to defer to agency interpretations of statutes with criminal implications in many contexts.[10] In Babbit v. Sweet Home Chapter of Communities, the Court distinguished its previous decision in United States v. Thompson/Center Arms. Co., which appeared to give credence to the theory that the rule of lenity superseded an agency’s interpretation of a statute with criminal implications. However, in Babbit, the Court clarified it has “never suggested that the rule of lenity should provide the standard for reviewing facial challenges to administrative regulations whenever the governing statute authorizes criminal enforcement.”[11] Nonetheless, as challenges to the bump stock ban have percolated through the courts of appeals, litigants have repeatedly raised the argument that the rule of lenity prohibits courts from deferring to an agency’s interpretation of a criminal statute.[12]

In advocating for the application of the rule of lenity, the respondent in Cargill invokes the two main justifications for the rule: notice and separation of powers concerns.[13] Noting that the ATF had previously taken the position that bump stocks did not qualify as machine guns, the respondent suggests that section 5845(b) fails to provide “fair warning that a bump stock is a ‘machinegun’ whose possession can result in a 10-year prison sentence.”[14] However, even ardent supporters of the rule of lenity, such as Justice Scalia, described “the proposition that the words of the United States Code or the Statutes at Large give adequate notice to the citizen” as “something of a fiction . . . albeit one required in any system of law.”[15] Instead, mere constructive notice is often sufficient for criminal liability.[16]  The use of notice-and-comment rulemaking to adopt the ATF’s 2018 interpretation of “machinegun” obviates any constructive notice concerns. The procedures required by the APA create a greater likelihood that affected parties will have actual, as opposed to constructive, notice of what constitutes criminal conduct. As Thomas Merrill has noted, “[a]dministrative rulemaking, at least in its modern guise, is subject to a much more unyielding set of procedural requirements” than legislative statute-making.

The respondent also briefly invokes separation of powers concerns, namely, the legislative supremacy argument that “[i]t is the role of Congress, not the courts or an agency, to write the laws and prescribe the circumstances under which the government may impose criminal penalties.”[17]  This argument is based on the view that, as a politically accountable branch, the legislature is more sensitive than the judiciary to society’s values, thereby placing it in a better position to determine which acts are worthy of moral condemnation.[18] However, in the context of notice-and-comment rulemaking, this argument is misplaced. The legislative supremacy justification for the rule of lenity was primarily a response to the fear that judges would usurp the role of the legislature by recognizing and enforcing federal common-law crimes,[19] an argument which is inapplicable when Congress has clearly delegated authority to define culpable conduct to an agency. When Congress has delegated its power, the delegated agency still must act within the bounds of Congress’s instructions.[20]

Relatedly, opponents of agency interpretations of criminal statutes fear that vesting both the crime-defining power and prosecutorial power in the Executive Branch may allow the promulgating enforcement agency to “shape substantive law to facilitate their targeting preferences.”[21] This argument was decidedly rejected in Touby v. United States, where the petitioners argued the Controlled Substances Act concentrated too much power in the Attorney General by giving them the authority to both schedule drugs and prosecute crimes, thereby violating the principle of separation of powers.[22] The Court clarified that “the principle of separation of powers focuses on the distribution of powers among the three coequal Branches; it does not speak to the manner in which authority is parceled out within a single Branch.”[23] Notice-and-comment rulemaking in particular, which is at issue in Cargill, is not subject to the same separation of powers concerns. As part of the Executive Branch, agencies are accountable to the public both through presidential elections and the processes by which they interpret statutes. Whereas unelected, life-tenured Article III judges may issue opinions with impunity, the Executive Branch is subject to change with every presidential election. 

Despite a favorable Fifth Circuit ruling,[24] the respondent in Cargill filed a brief in support of the government’s petition for certiorari, indicating their belief that the Court would be willing to address their expanded question presented and reach the issue of lenity. Indeed, Justice Gorsuch previewed his opinion on the matter in his statement denying certiorari to an earlier challenge to the bump stock ban, writing, “whatever else one thinks about Chevron, it has no role to play when liberty is at stake.”[25] Although, as the government argues, the Court may decide the matter without reaching the rule of lenity issue,[26] the opportunity to undercut the power of administrative agencies may prove too tempting to resist. 

Tess Saperstein is an Associate at Arnold & Porter. The views expressed in this piece are hers and do not represent the views of her employer. 


[1] 26 U.S.C. 5845(b).

[2] 26 N.Y.U. J. Legis. & Pub. Pol’y __ (forthcoming 2024).

[3] See Respondent’s Brief in Support of Certiorari at 24, Garland v. Cargill, No. 22-976 (“Cargill contends . . . that section 5845(b) unambiguously supports his position that non-mechanical bump stocks are not machineguns.”) and Brief for Petitioner at 17, Garland v. Cargill, No. 22-976 (“ATF correctly interpreted [the definition of a machinegun] and correctly determined that a rifle with a bump stock satisfies it.”). 

[4] Brief for Respondent in Support of Certiorari at 3, Garland v. Cargill, No. 22-976.

[5] Id. at i. 

[6] 26 U.S.C. § 5845(b) (2018).

[7] Bump-Stock-Type Devices, 83 Fed. Reg. 66514, 66518 (Dec. 26, 2018) (to be codified at 27 C.F.R. pts. 447, 478, 479).

[8] Id. at 66519. 

[9] Crandon v. United States, 494 U.S. 152, 177 (1990) (Scalia, J., concurring).

[10] See United States v. O’Hagan, 521 U.S. 642, 673-74 (1997) (granting the SEC’s interpretation of a statute with criminal implications ‘controlling weight’); INS v. Aguirre-Aguirre, 526 U.S. 415, 42425, 433(1999) (stating the court of appeals erred by failing to apply Chevron deference to the BIA’s interpretation in an immigration adjudication); c.f. Leocal v. Ashcroft,  543 U.S. 1, 11 n. 8  (2004) (stating, in dicta, that the rule of lenity “constrain[s] [the Court] to interpret any ambiguity in the statute in petitioner’s favor”)

[11] 515 U.S. 687, 704 n.18 (1995). 

[12] See Plaintiff-Appellant’s Brief-in-Chief at 39, Aposhian v. Wilkinson, 989 F.3d 890 (10th Cir. 2021) (“[I]f there were an ambiguity in the statute, the rule of lenity’s ‘fair warning’ requirement would forbid ATF from revising the statutory language through the Final Rule in such an unforeseeable way.”); Brief of Appellants at 21, Guedes v. ATF, 45 F.4th 306 (D.C. Cir. 2022) (“[B]ecause the definition of machinegun has direct criminal applications, Chevron deference is inappropriate and the rule of lenity applies instead to resolve any supposed ambiguities.”); Brief for Appellant at 16, Hardin v. ATF, 6. F.4th 895 (6th Cir. 2023) (“The rule of lenity ensures that Congress, which is most accountable to the people, establishes criminal sanctions, not an unaccountable bureaucracy, interested prosecutor, or remote judiciary.”).

[13] Brief for Respondent in Support of Certiorari at 28-29, Garland v. Cargill, No. 22-976. 

[14] Id. at 28. 

[15] United States v. R.L.C., 503 U.S. 291, 309 (1992) (Scalia, J., concurring) 

[16] Barlow v. United States, 32 U.S. 404, 411 (1833) (“It is a common maxim, familiar to all minds, that ignorance of the law will not excuse any person, either civilly or criminally.”).

[17] Brief of Respondent in Support of Certiorari at 29. 

[18] Daniel Richman, Defining Crime Delegating Authority–How Different Are Administrative Crimes?, 39 Yale J. on Reg. 304, 316-17 (2022)(“[I]n a liberal democracy, [criminal law] is supposed to express the moral condemnation of specific conduct by a community that speaks through its representatives.”)

[19] See United States v. Hudson & Goodwin, 11 U.S. (7 Cranch) 32, 34 (1812) (“The legislative authority of the Union must first make an act a crime, affix a punishment to it, and declare the Court that shall have jurisdiction of the offence.”)

[20] See J.W. Hampton, Jr., & Co. v. United States 276 U.S. 394, 409(1928) (stating that, for a delegation of authority to be constitutional, Congress must provide an “intelligible principle” to which the delegee must conform)

[21] Richman at 316. 

[22] Touby v. United States, 500 U.S. 160, 167 (1991)

[23] Id. at 167-68. 

[24] Cargill v. Garland, 5 F.4th 447 (5th Cir. 2023)

[25] Statement Denying Certiorari, Guedes v. Bureau of Alcohol, Tobacco, Firearms and Explosives, 140 S.Ct. 789, 790 (2020). 

[26] Brief for Petitioners at 16, Garland v. Cargill, No. 22-976 (“[The] rule [of lenity] comes into operation only if, after the application of all other tools of statutory interpretation, the statute remains grievously ambiguous. No such grievous ambiguity exists here.”).

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