What Did the Cargill Opinion Really Say?

This guest post does not necessarily represent the views of the Duke Center for Firearms Law.

The Supreme Court recently released its decision in Garland v. Cargill, the case about ATF’s bump stock ban – or more precisely, ATF’s 2018 classification of bump stocks as machine gun conversion devices under the National Firearms Act of 1934 (NFA).  In a 6-3 decision, the Court invalidated the regulation.  Justice Sotomayor wrote a dissent, which Justice Kagan and Justice Jackson joined. Justice Alito filed a concurring opinion.

The majority’s opinion was based entirely on statutory interpretation (that is, the meaning of the authorizing statute’s wording), and it concluded that a semiautomatic rifle with a bump stock did not fit within the statutory definition of a prohibited “machinegun.” With the rule invalidated, bump stocks are again legal under federal law. On the other hand, the Giffords Law Center reports that currently sixteen states and the District of Columbia have banned bump stocks, and those laws remain in force. Since the Court’s decision, the city of Philadelphia also banned bump stocks (see also here), and a bipartisan bill was introduced a bill in the Senate to ban bump stocks legislatively, which some Republican Senators blocked.  

I want to use this post mostly to clarify what the Court did not say or do in Cargill. First, the Court did not treat this as a Second Amendment case – there was no Second Amendment claim, the Second Amendment was not mentioned once in the opinions, and the case sets no precedent for future Second Amendment challenges to bump stock bans or other gun laws. The case was decided solely on the basis of the statutory language, and the statute itself was not being challenged in the case on constitutional or other grounds – rather, the challenge was about ATF’s rule that (re)interpreted that language to include bump stocks. (According to this earlier post by Andrew Willinger, it appears that no court has yet squarely addressed a Second Amendment challenge to a bump stock prohibition—including whether the devices, if textually protected, are nevertheless “dangerous and unusual.”)

Second, it is not completely accurate to say, as some headlines did after the decision, that “The Supreme Court just effectively legalized machine guns.” Of course, when aimed at people, bump stocks are extremely dangerous, allowing a mass shooter to spray a crowd with a hail of bullets, killing dozens indiscriminately, as happened in Las Vegas in 2017 (the incident that prompted the ATF to promulgate this rule). The Court left in place the federal statute that bans the manufacture or sale of (new) regular machineguns and requires expensive and time-consuming licensing for purchasing an old, pre-owned machinegun. Moreover, footnote 4 of the majority opinion leaves in place, and seemingly endorses, a separate ATF ruling letter that bans auto sear devices, which convert a semiautomatic firearm into a machinegun:

Machinegun variants of the AR–15 style rifle include an additional component known as an auto sear. The auto sear catches the hammer as it swings backwards, but will release it again once a new cartridge is loaded if the trigger is being held back. An auto sear thus permits a shooter to fire multiple shots while engaging the trigger only once. ATF has accordingly recognized that modifying a semiautomatic rifle or handgun with an auto sear converts it into a machinegun. 

It is worth noting that four days before the Court released Cargill, the Department of Justice announced the launch of “Operation Kill Switch,” aimed at machinegun conversion devices, and arrests under this crackdown have continued since the opinion came out. Crimes involving handgun conversion devices, commonly known as “Glock switches,” have increased in recent years (see also here).

It would be more accurate but less sensational to say that, in states where bump stocks are legal, shooters can simulate – but not replicate – machinegun fire with a semiautomatic rifle, and to that extent, legal bump stocks could undermine or thwart the purpose of the statute that prohibits machineguns. Even so, as I mentioned in previous posts, bump stocks have not been used in many mass shootings or even regular crimes, and I could find only one person who was prosecuted for illegal possession of a bump stock. (The case was quickly dismissed).

The footnote excerpted above brings me to a third important point about Cargill, which is ATF’s rulemaking authority. This point could have far-reaching ramifications for other pending challenges to recent ATF rules, such as its bans on pistol braces and “ghost guns.” It is only partly correct to say the Court held that the agency did not have authority to regulate bump stocks. In the lower courts, some gun-rights advocates had suggested that ATF lacks rulemaking authority, and this is not the case. Footnote 4 in Cargill explicitly mentions another ATF ruling, without questioning its validity, and the Court’s discussion of ATF’s approval of the Ithaca Model 37 shotgun (in the leadup to footnote 8) implies that ATF can issue valid rules and decisions about whether specific types of weapons fall under a statutory prohibition. Footnote 1 mentions other types of bump stocks not at issue in this case (mechanical bump stocks) and, if the Court was holding that ATF lacks any substantive rulemaking authority, the Cargill opinion would indeed have put other ATF rules at issue (courts have suggested that some administrative agencies lack such authority). On the other hand, Justice Thomas writes in his majority opinion,

Section 5845(b) defines a “machinegun” as any weapon capable of firing “automatically more than one shot . . . by a single function of the trigger.” We hold that a semiautomatic rifle equipped with a bump stock is not a “machinegun” because it cannot fire more than one shot “by a single function of the trigger.” And, even if it could, it would not do so “automatically.” ATF therefore exceeded its statutory authority by issuing a Rule that classifies bump stocks as machineguns. (emphasis added)

 “Therefore” is a crucial word here – Justice Thomas does not say that ATF exceeded its authority just because it issued a rule, but rather that it issued a rule that contradicts the relevant statute. “Exceeded its statutory authority” is standard jargon in administrative law that can refer to a variety of agency missteps, whether attempting to regulate an area not remotely under the agency’s statutory purview (say, if the Federal Communications Commission tried to regulate firearms), or attempting to regulate despite a specific statutory preclusion of regulating that topic (such as the law that prevents the Consumer Product Safety Commission from regulating guns or ammunition, though it can regulate nearly any other consumer product). “Exceeded its statutory authority” can also refer, somewhat confusingly, to an agency regulation on a permissible topic where the rule simply does not align with existing statutory terms or definitions for that subject – as happened here. It would have been a huge blow to ATF if the Court had held that the agency lacked rulemaking authority in general. To the agency’s relief, the Court did not do that. In theory, if Congress modified the wording of the relevant statute slightly – even without mentioning bump stocks – the agency could, in fact, promulgate a regulation banning bump stocks.

There are two other things the Court did not address that deserve mention. The various circuit court opinions in the bump stock cases discussed Chevron deference to agency interpretations and the rule of lenity, a traditional doctrine from criminal law. The Court addressed neither of these in its Cargill opinion, but it overruled Chevron in a separate case, Loper Bright v. Raimondo, two weeks after Cargill.   (of course, following the Court’s decision in Loper Bright, the circuit opinions that had upheld the ATF rule based on Chevron deference are no longer good law). In my administrative law course, I will teach Cargill together with Loper Bright, to illustrate how courts review agency interpretations of statutes in the absence of Chevron deference.

Justice Thomas mentions that the original Fifth Circuit panel had found the rule violated the rule of lenity (a rule that courts should construe statutory ambiguity in favor of the defendant), but the subsequent en banc decision from the Fifth Circuit held that the statute was “unambiguous,” and that holding is what Justice Thomas says the Court is affirming. If a statute is unambiguous, the rule of lenity does not apply.

It is also worth noting that Justice Alito’s concurring opinion seems to invite Congress to outlaw bump stocks, and Thomas’ majority does not express a view about that. Presumably, if Congress passed such a law, the Court would uphold it if challenged. Thus, Cargill is arguably a very narrow ruling – it says only that the current statutory definition of “machinegun” does not include non-mechanical bump stocks, but it does not reach further.

The three Justices who dissented basically read the statutory language differently and think it does cover bump stocks. Justice Thomas’ majority opinion is unusual in that it includes diagrams and a reference to an animated graphic, all attributed to the Firearms Policy Center’s amicus brief in the case. In her dissent, Justice Sotomayor pokes fun at this: “The majority looks to the internal mechanism that initiates fire, rather than the human act of the shooter’s initial pull, to hold that a ‘single function of the trigger’ means a reset of the trigger mechanism. Its interpretation requires six diagrams and an animation to decipher the meaning of the statutory text.”  

She has a point. Highly-credentialed and experienced appellate judges in various circuit courts have disagreed with each other, and internally on each panel, about whether the statutory language covers bump stocks, and the nine members of the Court disagree as well. In other words, reasonable, well-informed jurists can and do differ on the meaning of the relevant phrases in the law. While it is certainly legitimate for those in the majority to say that they think one interpretation is better or more plausible, it seems like an overstatement for the majority opinion to say (as the Fifth Circuit said) that the statute “unambiguously excludes such weapons.”  The majority could easily have reached the same conclusion without insisting that there was no other way to read the statute.

For more background: I wrote two posts about Cargill on this blog in anticipation of oral arguments here and here, as did Andrew Willinger here. In one of those previous posts, I wrongly predicted the Court would uphold the rule. Back in 2021, I wrote about other challenges to the bump stock rule on this blog here and here.  Jake Charles wrote here in 2019 about a separate case that unsuccessfully claimed the rule was an unconstitutional taking. I also co-authored a 2021 law review article about the early rounds of litigation over the bump stock ban, before the Fifth Circuit had decided Cargill, which deepened a circuit split over the issue.