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Upcoming Oral Arguments in the Bump Stock Case: What to Expect

  • Date:
  • February 9th, 2024

By: Dru Stevenson

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

The Supreme Court has scheduled oral arguments for February 28 in a challenge to the federal bump stock ban, Garland v. Cargill, in which the Fifth Circuit struck down the rule. There is now a circuit split on the issue, and the Supreme Court has been holding cert petitions in two other bump stock cases, Hardin (6th Cir.) and Guedes (D.C. Cir.).  Presumably, the Court will eventually remand Hardin and Guedes in light of its decision in Cargill. I co-authored a law review article about challenges to the bump stock rule back in 2021, though that was before Cargill or Hardin were decided at the circuit level.

All the circuit court opinions are based on two basic questions of statutory interpretation.  One question is whether the statutory language of 26 U.S.C. § 5845(b), which defines “machinegun” for purposes of other federal prohibitions, should apply to bump stocks; the other question, which is related, is whether Chevron deference should apply if the statute is ambiguous on this point. The circuit courts have reached different conclusions on each of these questions.  Cargill itself includes a dissenting opinion and two concurring opinions, and Hardin has a concurring opinion.  Though most readers may favor one side or the other as to the bump stock rule itself, it is worth bearing in mind that these are close enough questions to elicit a range of answers from different circuit court judges.

Note that the case is not presented as a Second Amendment challenge under Bruen, and the Supreme Court in recent years denied certiorari in three cases that had upheld the ban – Aposhian v. Garland (10th Cir.), GOA v. Garland (6th Cir. en banc), and Guedes (D.C. Cir.) – at an earlier procedural stage, even though those cases addressed the very same interpretive questions presented in Cargill.

My main purpose here is to clarify the technical legal issues presented, and to offer some predictions about what the Court will decide especially in light of the oral arguments the Court held recently in Loper Bright v. Raimondo, in which the Court was asked to end Chevron deference completely for all cases.

The first interpretive question about 26 U.S.C. § 5845(b), mostly comes down to the meaning of the phrase “by a single function of the trigger” in the definition of “machinegun.”  On the one hand, a shooter using a gun fitted with a bump stock pulls the trigger with their finger and holds it (applying continuous pressure), and the gun fires continuous rounds in rapid succession, reminiscent of a regular machine gun, until the shooter relaxes and lets the trigger return to its resting position.  On the other hand, the repeated firing occurs due to the “bumping” of the trigger finger from the gun’s recoil from the previous round fired, so in a sense, the trigger is being pulled (or pressed) again and again in very rapid succession, though it is not as fast as a regular machine gun.

The question, then, is whether to read the statutory phrase from the standpoint of the shooter, who is performing the same action – the same movement – with their trigger finger as they would with a regular machine gun (does “function of the trigger” mean “use of the trigger” or “human movement on the trigger”?), or whether to read it from the standpoint of the trigger component itself (is it being pulled/activated only once, or many times, regardless of how many human actions or movements are involved)? 

This type of interpretive question is not unique to this case, but fairly typifies the kind of difficult statutory interpretation question that courts must decide routinely, not only in firearms cases, but in products liability cases, patent infringement cases, and so on.  Consider, for example, United States v. Garcon, an Eleventh Circuit case from 2022 about the meaning of the word “and” in the First Step Act—a question controversial enough that the case includes multiple concurring and dissenting opinions. The Supreme Court, in Babbitt v. Sweet Home Chapter of Communities for a Great Oregon, faced a difficult statutory interpretation issue with the work “take” in the Endangered Species Act.  In Nix v. Hedden, the Supreme Court had to decide whether the word “fruit” in the Tarriff Act included tomatoes. The Seventh Circuit in Continental Can v. Chicago Truck Drivers wrestled with the question of whether the statutory phrase “substantially all” meant more than half, or eighty-five percent, in the context of a law about employee pension funds. And in United States v. Locke, the Supreme Court had to parse the statutory phrase “prior to December 31” in a high-stakes case about filing deadlines with the Bureau of Land Management.

Courts have also had to interpret the phrase “single function of the trigger,” from the statutory definition of “machinegun,” outside the context of the bump stock rule.  In 2020, a federal district court in United States v. Babbitt observed that “[o]ther courts have interpreted the phrase ‘single function of the trigger,’ and for decades have found that the ordinary meaning of the phrase looks to the shooter’s action in pulling the trigger . . . .” The Babbitt opinion, which is not about bump stocks, surveys cases along these lines, and includes an interesting discussion of the legislative history of the “single function of the trigger” phrase in the original National Firearms Act.

If a court finds that either reading of the statute is at least somewhat plausible, even if it thinks one reading is more plausible, it then must address whether to favor the reading that would be to the disadvantage of the government under a traditional legal doctrine called the “rule of lenity.” The rule of lenity applies in criminal cases and directs courts to interpret ambiguous criminal statutes in favor of the defendant. (Here is my short video explainer about the rule of lenity and statutory interpretation).  As simple as that may sound, the rule of lenity is unpredictable in practice, because judges often disagree about whether a statute is clear or ambiguous (numerous circuit court judges have now disagreed about whether the phrase “single operation of the trigger” is clear or ambiguous), and about how much ambiguity must be present to trigger the application of lenity.  Another problem with applying the rule of lenity in the bump stock cases is that the rule traditionally operates as a defense to criminal charges, while these cases are all preemptive, pre-enforcement challenges to the validity of the statute.  That is a very unusual, if not novel, context in which to raise a lenity-based argument. None of the challengers in the bump stock cases are facing criminal prosecution.  

The only case I can find of anyone being prosecuted for possessing a bump stock is a military prosecution, United States v. Alkazahg, which did apply the rule of lenity and reversed the conviction.  Alkazahg also addressed another issue with the rule of lenity – most of the cases discussing it premise the rule, at least in part, on the lack of notice to the citizenry about what the statute in fact prohibits. Alkazahg was fully aware of the ATF’s bump stock rule before his arrest (as are those bringing preemptive challenges to the rule), but the court decided that “notice” did not matter in the case because it said that Congress has been unclear about whether bump stocks are prohibited. If the Supreme Court decides to apply the rule of lenity in the pre-enforcement challenge in Cargill, it will be a significant development in criminal law overall that could affect many types of crimes (at least in federal court, and if they link it to due process concerns, it could affect state courts as well).  The Fifth Circuit said that the rule of lenity should apply, as did the Sixth Circuit in Hardin.

The other main interpretive question is whether Chevron deference applies.  Chevron is a longstanding rule that directs courts to give deference to reasonable agency interpretations of ambiguous statutes (including questions on which the relevant statute is silent), premised on the idea that Congress intended the experts at regulatory agencies to fill in the details of the general laws entrusted to that agency for implementation and enforcement.[1] Government agencies usually win if a court gives Chevron deference, but they might have won a lot of those cases anyway, even without Chevron (this is the subject of an ongoing academic debate).  There are two confusing issues with applying Chevron here, even if Chevron remains good law after this term.

First, when the bump stock rule was first promulgated in 2017, the ATF/DOJ did invoke Chevron deference.  But when the first rounds of legal challenges to the rule came, the DOJ expressly waived Chevron deference, saying that the statute itself clearly prohibited bump stocks, so there was no ambiguity that would even raise the question of deference.  There is a longstanding split of case authority on whether Chevron applies regardless of whether the government agency is asking a court to apply it.  The D.C. Circuit, which decides more administrative law cases than any other circuit and carries a lot of clout in the area as a result, held in Guedes that Chevron applies even without the government invoking it, and even if the government waives it (these are separate questions), as did the Sixth Circuit in a previous bump stock case, GOA v. Barr, and the Tenth Circuit in Aposhian v. Barr.

The second issue is whether Chevron applies to regulations that carry criminal penalties, like the bump stock rule.  Chevron deference usually comes up in civil regulatory cases, such as pollution regulations.  There are cases – including Supreme Court cases – pointing each way on the question of whether the doctrine applies to regulations that can carry criminal penalties, but it is an unsettled question of law. Some of the circuit court judges who have written opinions in the bump stock cases (often in concurring or dissenting opinions) have said that Chevron should not apply when incarceration is possible, even if the doctrine is good law for other types of regulatory cases.

It is possible that the Supreme Court took the case to settle one or both of these two outstanding questions about Chevron deference, even if they keep Chevron intact for most cases. It is also possible that they took the case to say that the statute itself (the “single function of the trigger” phrase) is clear one way or the other, in which case it would not have to reach the Chevron questions at all.

As mentioned above, the Supreme Court recently heard oral arguments in the Loper Bright case, which presents the Court with an opportunity to overturn Chevron once and for all, in its entirety.  This could impact the Cargill case, which presents (along with the other interpretive questions outlined above) the question of whether Chevron should apply.  In fact, I think the fact that the justices agreed to take the Cargill case – after denying cert in at least three previous cases that upheld the bump stock ban – is a hint that a majority of the Court is not planning to kill off Chevron deference yet. If it had already become clear in their conferences and private conversations that Chevron was doomed, I believe they would have just held Cargill to be remanded and decided in light of Loper Bright, just as they have held Hardin and Guedes to be decided in light of Cargill. On the other hand, it is possible that they could decide Chevron is dead, but that the statute is clear that bump stocks are machineguns (the opposite of what the Fifth Circuit held).  But if they were going to do that, it seems to me they would have granted cert in one of the previous bump stock cases to say that Chevron did not apply, but the statute clearly authorized the bump stock ban.

It is far from certain what the Court will do with Chevron. I have followed lively discussions between dozens of well-known administrative law experts, and while they hold a range of views about the virtues of Chevron (and about what it really means), there was a general consensus after oral arguments in Loper Bright that the Court is likely to “Kisorize” the doctrine.[2]  Kisor v. Wilkie was a 2018 case that involved another type of judicial deference for agencies, called Auer deference, which applies for agency interpretations of their own regulations, as opposed to agency interpretations of Congressional statutes, which is the domain of Chevron. Rather than jettison Auer deference completely, as many Court watchers expected, the Court simply complicated it by adding several factors courts should consider in deciding whether to apply such difference.  Judge Kagan wrote the majority opinion in Kisor.  Most administrative law professors expect the Court will do something similar in Loper Bright, keeping Chevron but limiting it with some new factors (it is unclear at which Chevron step such factors would apply).  Connecting the case to Cargill, and given the apparent inclination of the Court to narrow Chevron, I would not be surprised if the Court decided to use Cargill to say that Chevron deference never applies when criminal sanctions are at stake, or that it does not apply unless the government asks for it, or both. Neither of these questions are presented in Loper Bright, so the Court could use Cargill in tandem with that case to establish some new boundaries for Chevron.

One of the Kisor factors most likely to be applied to Chevron is some kind of judicial scrutiny when an agency reverses itself on a question of policy, which happens often (most often due to a change in which party is in the White House – I am not aware of any case where an agency changed its interpretation back and forth from case to case in a short period of time). This is an issue mentioned in the bump stock cases, because the ATF approved the manufacture of bump stocks for several years in a number of private opinion letters and similar informal guidance documents.  It would be unprecedented, however, for a court to hold that an agency can never take a different approach once it has permitted something for individual parties – agencies do this all the time. The ATF had never promulgated a bump stock rule via notice-and-comment before 2017, and the legal status of the private opinion letters predating that is very different (and those letters would not normally count as binding law on the agency for other cases).

That being said, my prediction, based on the previous cert denials, is that the Court will reverse the Fifth and Sixth Circuit on simple statutory interpretation grounds, and hold that the “machinegun” statute clearly includes bump stocks as a type of conversion device, and then say that Chevron is not applicable because the statute is clear. 

Breaking it down to individual Justices – I expect Kagan, Sotomayor, and Jackson to be safely on the side of upholding the bump stock ban, regardless of whether Chevron applies.  Based on the patterns of previous cert denials, and their concurrence in Bruen, I expect Roberts and Kavanaugh to think either that the statutory language favors the ATF, or that the ATF’s interpretation of it is reasonable if Chevron applies. Barrett is harder to predict, but her previous opinions about guns – including her Kanter dissent while on the Seventh Circuit – may suggest that she views the legitimacy of various restrictions at least partly through a lens of “dangerousness,” in which case I think she is likely to view bump stocks as unreasonably dangerous and the type of device Congress intended to ban under the NFA. Justice Gorsuch has already signaled his position that Chevron should not apply in the case, but claimed to be agnostic about the merits. I would consider him a toss-up; on the one hand, his statement accompanying the previous denial of certiorari in Guedes expressed concern about an agency being able to criminalize something it previously considered legal.  On the other hand, he may decide to maintain consistency with the interpretation most courts have used for decades that treats “function of the trigger” as synonymous with “pull of the trigger” in cases not involving bump stocks.  I am uncertain about what Thomas and Alito will think about this case, but I ultimately think that a majority of the Court will uphold the rule on simple statutory interpretation grounds and will either not reach the Chevron issues or declare that Chevron does not apply.



[1] Note that agencies were getting some level of such deference long before the Chevron case, but the latter set forth a simple two-part test that mostly replaced the tradition of weighing several factors in deciding whether an agency is correct.

[2] Justice Barrett used that term during oral argument.