What Questions Should We Expect During Oral Arguments in Garland v. Cargill?

  • Date:
  • February 14, 2024

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


Oral arguments in Garland v. Cargill, which is a challenge to the ATF’s six-year-old bump stock rule, are set for February 28.  Based on the issues presented in the case and the current circuit split, the following are questions I expect the justices might ask during oral arguments.  I outline the issues presented in the case in a separate post here.  I group the questions by the side to which they would be directed if asked in a challenging way; of course, sometimes justices ask a “friendly” or softball question, which would be a more challenging question if posed to the opposing party.


I expect few or no questions about the Second Amendment or historical gun laws from the Founding era – the questions on appeal focus on the statutory definition of “machinegun” and the ATF’s rule interpreting the statutory verbiage.  In a nutshell, I expect most of the questions to focus on the ATF’s rulemaking authority, its interpretation of 26 U.S.C. § 5845(b) (which has changed over time), what Congress could authorize ATF or other agencies to do going forward, and if/how Chevron deference should be applied in cases like this.





1.      If the statute is clear, how does ATF explain its previous opinion letters approving bump stocks? 


(During the Obama Administration, the ATF issued private decision letters to ten or so manufacturers, giving legal approval for their bump stock designs.  The policy reversal after the mass shooting in 2017 has come up repeatedly in various legal challenges to the bump stock rule.  On its website, ATF succinctly explains this reversal in one paragraph. In administrative law, abrupt policy reversals by regulatory agencies are not unusual, nor are they prohibited, but they sometimes invite extra judicial scrutiny—the agency must offer a justification for the change.  Agencies change interpretations either because of turnover in the White House, or because of new technologies or major changes in society.  The most famous case about agency policy reversals is Motor Vehicle Manufacturers Association v. State Farm, which was about seatbelt and airbag requirements in cars, and in which the agency had changed the rules repeatedly over the course of two decades.)


2.      Did previous ruling letters warn manufacturers that they were subject to rescission or to possibly being superseded by new regulations, at any time? What if manufacturers rely on private opinion letters from the agency and invest millions of dollars in producing the seemingly-approved product?


(This is not dispositive to the case, but the issue of parties relying on an agency’s official statements, and then being surprised by a policy reversal, is one factor courts sometimes consider.  Some agencies include boilerplate disclaimers in their private letter rulings or other guidance documents that the document is not binding on the agency in the future and is not legally binding with respect to other parties. An example would be the customs determination letters at issue in the seminal case United States v. Mead. But not all agency private letter rulings explain this clearly.)

3.      Is there any limit on what ATF could define as a conversion device?  Or, put another way, is there any limit on what items the ATF could ban by adopting a novel interpretation of the National Firearms Act?


(The government lawyer’s best answer to this question would be to freely admit that ATF is constrained by the statute and by judicial doctrines about agency interpretations generally.  Agencies are constrained by the provisions of the statutes they are responsible for implementing.  Many statutes include inherently ambiguous terms, like “reasonable” or “substantial,” and statutes are often silent on many details about implementation and enforcement.  Historically, the Supreme Court has found that agencies have some latitude to interpret ambiguity and fill in the details, but there are several lines of cases setting boundaries on such agency discretion – including “Step Two” of Chevron deference, which requires agency interpretations to be “reasonable.”  There are a number of cases where the FDA or FTC maintained for decades that they lacked statutory authority to promulgate certain types of rules, only to decide at some point that they had, in fact, had such authority all along.)

4.      If bump stocks clearly fit under the statutory language, as the government argued in lower courts, why was the rule even necessary?  Couldn’t ATF have simply started enforcing the “machinegun” prohibition against bump stock owners, sellers, and manufacturers?


(ATF has been enforcing the “machinegun” prohibition over other conversion devices, such as autoshears or “Glock switches,” without promulgating a rule – instead, it argues at trial that the device clearly violates the statute.  In the bump stock cases, ATF has been arguing that bump stocks clearly violate the statute.  I expect the government lawyer to answer that promulgating a rule was necessary because the agency had previous approved some of these devices, but after seeing one of its approved devices in use in the 2017 Las Vegas massacre, the agency realized its previous interpretation was incorrect.)

5.      The next time a change happens in the presidency, could the ATF suddenly rescind the current rule and legalize bump stocks?  Could the rule switch back and forth every time there is a new administration?


(In theory, each new president can direct an agency to rescind rules adopted by a previous administration. Changing or rescinding a rule takes a long time, usually a few years.  Some of the leading cases about agency rules, such as Chevron and State Farm, were actually about Reagan-era deregulation actions by agencies, reversing policy from the Carter years.  Rule changes face immediate legal challenges in court – whether from the regulated industry, or from advocacy groups who want stricter rules – and courts can delay the implementation of a rule change, or can settle a legal question so that the agency cannot revisit the issue.  In addition, under the Congressional Review Act, if Congress passes a resolution to undo an agency action, and the President signs it, the agency is precluded from trying to do the same thing for at least five years, which will spill over into the next administration.)

6.      Apart from the Las Vegas mass shooting, which was unique in many ways even among historical mass shootings, have bump stocks been used in other mass shootings, or even a lot of regular homicides?


(The answer appears to be no – as far as I can tell, bump stocks were not used in mass shootings apart from Las Vegas in 2017.  In its rule, ATF did not cite any other instances of bump stocks being used in mass shootings or even single homicides.)

7.      Haven’t bump stocks become mostly obsolete with the now-widespread availability and low cost of “autoshear” devices, a.k.a “Glock switches”?  Would invalidating the bump stock rule result in more homicides involving bump stocks?


(As the New York Times reported in 2022, Glock switches have become increasingly common, are inexpensive, and are used in some mass shootings.  On the other hand, they normally work with semiautomatic handguns, not semiautomatic rifles.  Handgun homicides are far more common than homicides with rifles, including AR-style rifles, so Glock switches will likely remain far more common, even if bump stocks are legalized.  On the other hand, rifles are the weapon of choice for certain circumstances, so mass shootings involving rifles are more likely to involve bump stocks, if they were available, than Glock switches.)

8.      Should an agency be able to waive Chevron deference, either tacitly or expressly?  If so, can an agency change its position about invoking Chevron deference between promulgating a rule and defending the rule, as it did here?


(This is an unsettled question in administrative law – one that the Supreme Court will need to answer at some point if Chevron survives after this term.)

9.      Should Chevron deference apply to interpretations of criminal statutes?  Could the Department of Justice, or the Drug Enforcement Agency, reinterpret a section of the Controlled Substances Act, and then ask for Chevron deference?


(This is also an unsettled legal question – there are Supreme Court cases that seem to point both ways on this issue and none of them squarely addressed the question.)

10.  Suppose we take the fact that circuit court judges have reached opposite conclusions about the meaning of this statute as prima facie evidence that there is at least some ambiguity present in the language – in that case, should the Court then give any weight (or any type of deference) to the agency’s interpretation?  If so, what type of deference?


(In some cases, if a court decides that Chevron does not apply, it still applies Skidmore deference to the agency’s interpretation.)


11.  Follow-up question: if we (a majority of the Court) conclude that the statute has some ambiguity about the definition of “machinegun,” would the rule of lenity apply, and render the ATF rule unenforceable? 


(As I explain in a companion post to this one, the rule of lenity applies in cases of statutory ambiguity but normally arises as a defense in criminal prosecution, not preemptive challenges to new regulations – it is not clear how the Supreme Court would view this.)


12.  If we do not apply Chevron deference, should we apply “hard look” review under State Farm v. Motor Vehicles Manufacturers, given the agency’s reversal of its own position on this policy?  Would the bump stock rule survive “hard look” review?


(“Hard look” review is a type of heightened judicial scrutiny courts apply to certain agency actions, especially abrupt policy reversals.  “Hard look” review is not, however, a balancing test or a type of constitutional scrutiny – rather, it applies a critical look at whether the agency adequately explained its rationale for its new policy, including an exhaustive consideration of policy alternatives – see FCC v. Fox Television Stations.)





1.      Your position is that Congress should decide this issue, but doesn't the Congressional Review Act (CRA) give Congress an easy, streamlined route to block any regulations it finds objectionable, by a simple bicameral resolution and presidential signature?  Doesn’t the CRA give Congress enough control over ATF rulemaking, and a check on rules that do not reflect congressional understanding of the statute?


(Congress now routinely invokes the CRA to invalidate recent agency rules or actions whenever a single party controls both chambers and the White House.)


2.      Wouldn’t all the same concerns about potential surprise from policy reversal apply to Congress abruptly amending the statute?  How would that be better for the bump stock owners or sellers?


(In theory, there is no legal limit on how often Congress can amend or repeal statutes. In practice, statutory repeals are relatively rare, and take a long time, especially during committee review and especially compared to agency policy changes.) 


3.      If Congress were to amend the statute, could it expressly say in the statute that any product ATF deems to be a machinegun conversion device would fall under the statutory prohibition?  Or, alternatively, could Congress expressly authorize ATF to determine what counts as a “single function of the trigger”?  (Or, to put it another way, could Congress amend the statutory definition to say bump stocks count as a machinegun conversion device, and then expressly authorize ATF to define what counts as a “bump stock”?)


(Historically, Congress could have done this and did similar things with other agencies – but there has been a movement in recent years to rein in congressional delegations to agencies, so it is not clear what the current Court would say.)

4.      Could Congress authorize the ATF to make rules classifying new products as falling under National Firearms Act prohibitions, so long as it also specified the agency has to go through a rigorous, prolonged publication and public comment process, and be subject to judicial review under the APA?  Or could Congress expressly authorize the agency to promulgate the same rule it did here, but require the agency to use the more difficult formal rulemaking procedures set forth in Sections 556-557 of the Administrative Procedure Act?


(The former is in fact what Congress already requires, and what the ATF/DOJ in fact did here.  The latter is what Congress has done to some other “disfavored” agencies with regard to agency rulemaking.)


5.      Could ATF publish a manual, updated yearly, listing dangerous or potentially illegal guns and gun accessories, and could Congress simply incorporate the manual by reference in the statute?  If not, would our holding in this case affect Congress’ ability to incorporate other sources by reference into federal statutes, such as building codes?


(Incorporation by reference of outside sources, or regulations, is fairly common in statutes, especially on the state level—industry-association fire or safety codes are a common example – but sometimes in federal laws as well.  In addition, many federal statutes incorporate state law, usually by reference, and state laws routinely incorporate federal laws and regulations by reference. The reference can be specific – such as to a specific code section – or general – such as “prohibited by federal/state law.”)


6.      Can other regulatory agencies, like the IRS or the Department of Homeland Security, define terms or fill in details of their statutes, in other areas of law?  Is there some reason ATF should not be able to do what other agencies are doing? Or, to put it differently, would the decision in this case set precedent that would affect other areas, like the tax code or bank regulations? 


(Cargill’s lawyer needs to tread carefully with this issue – there is a long history of the IRS interpreting tax laws via published rules, and the same is true for other agencies that are less controversial than ATF, such as those regulating federal banks or the stock market.)


7.      Does ATF have any interpretive authority as to the National Firearms Act?  If not, is it because the relevant statutes are clear in every respect, or because the ATF should be singled out as not having any rulemaking authority, as opposed to other federal agencies?


(The courts that have sided with ATF in the bump stock cases have cited statutory provisions expressly giving interpretive authority to the Attorney General for the Gun Control Act, and the AG at least nominally promulgates ATF rules.  Even so, it is not clear whether such interpretive authority applies to everything in the federal gun statutes, or only to provisions or terms identified by Congress as under the AG’s interpretive discretion.)

8.      Could Congress solve the problem presented here by separating the rulemaking function from enforcement, in terms of which agencies are involved?  For example, could it expressly authorize an agency like the Federal Trade Commission or the Department of Commerce to severely restrict the sale of products it deems to be machinegun conversion devices, but entrust enforcement to the ATF as a separate agency?


(This issue has not come up in the lower courts, but it is something that occurs in other areas of law. For example, the Army Corps of Engineers defines what counts as federally protected wetlands, but most of the enforcement of the relevant rules falls to the EPA.  A similar pattern occurs with the Endangered Species Act – the Fish & Wildlife Service lists or delists animals as “endangered,” but enforcement of the ESA is typically handled by the EPA.)

9.      Is Cargill claiming that ATF did not comply with statutory rulemaking requirements under the Administrative Procedure Act?  Or, did the agency fully comply with all the public notice and comment requirements of APA Section 553, as well as judicial glosses on the APA, about agency rulemaking?


(This claim has not been made, as far as I know – but admitting the agency fully complied with the APA procedural requirements for public notice and comment would undermine the argument that ATF’s policy reversal constitutes a “surprise” or that it suddenly makes bump stock owners into “criminals.”)

10.  If an agency, such as the Internal Revenue Service or the Immigration and Customs Enforcement, has previously interpreted a statute one way in a few dozen private opinion letters, is the agency forever barred from promulgating a rule of general applicability that interprets the statute differently?


(The answer is surely no – agencies do this all the time – but some of the arguments by gun rights groups in these cases have seemed to verge on such a claim.)

11.  How many people have been prosecuted under the new bump stock rule?  Is there any evidence of actual agency overreach here in practice; that is, in terms of enforcement?


(It appears that prosecution for bump stock possession is rare or currently nonexistent, except for a handful of cases involving multiple gun charges in which a bump stock was just one item in a large cache of illegal weapons the defendant possessed.) 


12.  If we decide to apply Chevron deference to the agency’s interpretation, do you still win?  If so, at Step 1 or Step 2?


(Even if the Court decides to apply Chevron, Cargill has an opportunity to argue against the ATF at each step.  At Step 1, he could argue that the statute clearly allows bump stocks; at Step 2, he could admit the statute is unclear, but still argue that ATF rule is not a reasonable interpretation of it.)


13.  If we conclude Congress has already authorized the agency to promulgate rules like this, should we apply “hard look” review under State Farm, due to the agency’s reversal of its policy position?  Would the agency win under hard look review?


(ATF’s policy reversal about bump stocks is distinguishable from the reversals in State Farm, because ATF’s prior approval of bump stocks never went through notice-and-comment rulemaking or had the status of a “regulation.”)