Legal Sidebari
Is ATF’s Bump-Stock Ban Lawful? Circuit
Courts Are Split
February 15, 2023
Congressional interest in “bump-stock” devices—accessories that allow rifles to effectively mimic the
firing capabilities of a fully automatic weapon—grew after authorities discovered that the perpetrator of
the October 2017 mass shooting in Las Vegas had attached them to several of his semiautomatic firearms.
Federal legislation does not expressly regulate bump stocks. At the administrative level, the Bureau of
Alcohol, Tobacco, Firearms, and Explosives (ATF) banned these devices—effective March 26, 2019—in
a final rule published in the Federal Register. ATF accomplished this ban by classifying bump-stock
devices as “machineguns,” as that term is defined in the National Firearms Act of 1934 (NFA) and the
Gun Control Act of 1968 (GCA). Several bump-stock owners and advocates challenged ATF’s rule in
multiple lawsuits, arguing, among other things, that ATF promulgated the rule in violation of the
Administrative Procedure Act (APA). In a series of decisions between 2019 and 2022, the U.S. Courts of
Appeals for the Tenth and D.C. Circuits rejected APA challenges to the rule, and the Sixth Circuit divided
evenly in a case that resulted in affirmance of a district court ruling upholding the rule. In contrast, on
January 6, 2023, the Fifth Circuit, sitting en banc, held that the rule violates the APA and that an act of
Congress is required to prohibit bump stocks, creating a circuit split with the earlier decisions. This
Sidebar explains the statutory framework for regulating machineguns, discusses ATF’s final rule, and
examines the APA-related litigation that has resulted in a circuit split.
Statutory Regulation of Machineguns
Machineguns are separately regulated by the NFA and the GCA; both statutes rely on the definition found
in the NFA:
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. The term shall also include the frame or receiver of any such weapon, any part
designed and intended solely and exclusively, 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 if such parts are in the possession or under the control of a person.
The NFA imposes various taxes on the importation, manufacture, and transfer of covered firearms like
machineguns and requires registration with the Attorney General. The GCA, as amended by the Firearms
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Owners’ Protection Act (FOPA), makes it unlawful to transfer or possess a machinegun subject to two
exceptions: (1) transfers to or from, or possession by (or under the authority of), federal or state
authorities; and (2) the transfer or possession of a machinegun lawfully possessed before the effective
date of the act (May 19, 1986). FOPA’s machinegun ban is codified at 18 U.S.C. § 922(o).
Before ATF promulgated its final rule regarding bump stocks, the agency via a policy statement had
interpreted the phrase “automatically ... by a single function of the trigger” in the NFA’s definition of
“machinegun” to cover devices enabling a weapon to shoot “more than one shot, without manual
reloading, by a single pull of the trigger.” Still, before issuing the final rule, ATF had not treated bump-
stock devices as a single, homogenous category of firearm accessory. Rather, in previous determinations
responding to classification requests as to whether a bump stock converts a semi-automatic firearm into a
machinegun, ATF had reached different conclusions for different bump-stock devices based on how each
device uniquely functioned.
2018 ATF Final Rule
In its final rule, ATF examined various “bump-stock-type-devices,” including “‘bump fire’ stocks, slide-
fire devices, and devices with certain similar characteristics.” ATF characterized covered devices as
replacing a rifle’s standard stock and allowing the rifle to slide back and forth rapidly by harnessing the
energy from the firearm’s recoil.
In concluding that bump-stock-type devices are machineguns, ATF’s final rule construed two terms in the
NFA and GCA’s definition of “machinegun”: (1) “automatically,” and (2) “single function of the trigger.”
ATF explained in the final rule that it understood “‘automatically’ as it modifies ‘shoots, is designed to
shoot or can be readily restored to shoot’” to mean “functioning as the result of a self-acting or self-
regulating mechanism that allows the firing of multiple rounds through a single function of the trigger.”
ATF, in turn, defined “single function of the trigger” as “a single pull of the trigger and analogous
motions.” So defined, ATF concluded that a bump-stock device is a machinegun because it “allows a
semi-automatic firearm to shoot more than one shot with a single pull of the trigger by harnessing the
recoil energy of the semi-automatic firearm to which it is affixed so that the trigger resets and continues
firing without additional physical manipulation of the trigger by the shooter.” ATF also determined that
bump-stock devices governed by the rule were created after FOPA’s effective date. Therefore, because
the statutory definition of machinegun, as interpreted by ATF, encompasses bump-stock devices, those
firearm accessories could no longer be possessed or transferred after the rule’s effective date.
Prior Appellate Caselaw Regarding ATF Bump-Stock Rule
After ATF issued the final rule, several bump-stock owners and organizational advocates filed lawsuits to
block the rule from taking effect. They contended, among other things, that ATF lacked statutory authority
to promulgate the final rule and, thus, violated the APA. Between 2019 and 2022, the U.S. Courts of
Appeals for the Sixth, Tenth, and D.C. Circuits considered APA challenges filed in their respective
jurisdictions. These APA rulings mostly hinged on the circuit courts’ application of the administrative law
doctrine commonly called “Chevron deference,” in reference to the Supreme Court opinion responsible
for its genesis, Chevron U.S.A. Inc. v. Natural Resources Defense Counsel. In that case, the Supreme
Court announced a two-part framework for evaluating an agency’s interpretation in a “legislative rule” of
a statute it administers. At step one, courts determine whether an agency-administered statute is
ambiguous. If so, courts proceed to step two, asking whether the agency’s statutory interpretation is
reasonable. Courts uphold (and thus defer to) a reasonable agency interpretation, even if it is not
necessarily the best or most reasonable available interpretation of the statute.
In the 2019 case Guedes v. ATF, a D.C. Circuit panel applied these principles to uphold ATF’s bump-
stock rule in a divided decision on the APA issue. The panel’s majority concluded that the bump-stock
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rule is a legislative rule to which Chevron analysis applies, determining in the process that Chevron
deference can be applied to agency interpretations of statutes with criminal law implications (an issue that
has been the subject of some judicial dispute). In so doing, the appellate court reasoned that the Supreme
Court has previously applied Chevron deference to agency interpretations of statutes with criminal law
implications, including in the original Chevron case and in the federal securities law context as well.
Next, the D.C. Circuit applied the two-step Chevron framework to ATF’s rule and concluded that (1) the
two terms at issue (“automatically” and “single function of the trigger”) are ambiguous, and (2) ATF
reasonably interpreted those terms. As for the phrase “single function of the trigger,” the court decided
that the term is capable of two interpretations, neither of which is compelled. Under one interpretation,
which would exclude bump stocks, the term would mean “a mechanical act of the trigger.” Under a
different interpretation, which would encompass bump stocks, the term would mean “a single pull of the
trigger from the perspective of the shooter.” Thus, the court concluded that, “[i]n light of those competing,
available interpretations, the statute contains a ‘gap for the agency to fill.’” The court then held that ATF’s
reading is permissible, commenting that ATF “is better equipped than we are to make the pivotal policy
choice between a mechanism-focused and shooter-focused understanding of ‘function of the trigger.’”
For the term “automatically,” the court similarly concluded that the term is capable of multiple
interpretations. The court opined that the term can include some human involvement, rejecting the
plaintiffs’ contention that “a gun cannot be said to fire ‘automatically’ if it requires both a single pull of
the trigger and constant pressure on the gun’s barrel, as a bump-stock device requires.” The court
reasoned that a single pull of the trigger combined with constant pressure on the trigger is “a quite
common feature of weapons that indisputably qualify as machineguns.” The court next concluded that
ATF’s construction of “automatically” is permissible because, by also requiring a “self-acting or self-
regulating mechanism,” the definition “demands a significant degree of autonomy from the weapon
without mandating a firing mechanism that is completely autonomous.”
Following Guedes, the Tenth Circuit issued a similar ruling upholding ATF’s bump-stock rule.
Additionally, after a district court in the Sixth Circuit upheld the rule, the en banc Sixth Circuit evenly
divided on the issue, resulting in the affirmance of the district court’s ruling. The opinions in support of
affirmance in that case determined that ATF’s interpretation of “machinegun” was entitled to Chevron
deference and that even without such agency deference, the rule set out the best interpretation of the
statute using ordinary tools of statutory construction. The D.C. Circuit revisited the bump-stock rule in
2022 in Guedes II (having been denied a preliminary injunction, the plaintiffs in Guedes then appealed
from the district court’s grant of summary judgment in favor of ATF) and this time a panel upheld the rule
without relying on the Chevron framework. The court concluded there was “no need to decide what
deference, if any, [the] regulation should receive” because “the agency’s interpretation of the statute is the
best one,” meaning the rule was lawful.
Fifth Circuit Decision Creating a Circuit Split
On January 6, 2023, the en banc Fifth Circuit held that ATF’s bump-stock rule is unlawful, splitting with
the circuits that had upheld the rule. Twelve of the sixteen Fifth Circuit judges determined that, even
assuming the relevant statutory terms were ambiguous, the rule of lenity—a canon of construction under
which interpretive ties concerning ambiguous criminal statutes tip in favor of the defendant—would
apply, meaning that the definition of “machinegun” should be construed narrowly to exclude the bump-
stock devices at issue. In disagreement with the 2019 Guedes panel’s conclusion, the en banc majority
further reasoned that Chevron deference does not apply to agency interpretations of statutes (including
ATF’s bump-stock rule) with criminal law implications, adding that legal obligations carrying criminal
liability should come in the form of a statute from Congress, and not a rule from an administrative agency.
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Eight judges also would have held, in contrast to the Sixth, Tenth, and D.C. Circuits, that the statutory
terms “automatically” and “single function of the trigger” are unambiguous, that they do not warrant
Chevron deference, and that they do not by their own terms cover the devices at issue. If the terms were
ambiguous, the judges asserted that Chevron deference still would be unavailable because the government
waived the argument, the rule imposes criminal penalties, and the rule is inconsistent with ATF’s prior
treatment of bump stocks. Whereas their sister courts viewed a user-focused perspective as an available
interpretation of the statutory language supporting ATF’s rule these judges focused on what they viewed
as the statute’s unambiguous reference to “the movement of the trigger itself, and not the movement of a
trigger finger.” So oriented, the judges described the function of the devices at issue: an individual pulls
the trigger, leading to the firing of a single shot; subsequent shots are possible only when the user
“maintain[s] manual, forward pressure on the barrel and manual, backward pressure on the trigger ledge.”
According to the judges, multiple shots from the bump-stock devices at issue depend on additional action
and thus are not “automatic”; moreover, multiple shots still require multiple functions of the trigger itself,
not a “single function” as the statute requires.
Three judges dissented. The judges objected to the majority’s application of the rule of lenity, arguing that
the majority impermissibly lowered the bar for when the rule should apply and thereby usurped the power
of Congress to define federal crimes.
Considerations for Congress
Given the current split of authority regarding the legality of ATF’s bump-stock rule, there is room for
congressional action if Congress deems it appropriate to restrict public access to bump stocks via
legislation. In light of ATF’s (and some federal courts’) conclusion that the terms “automatically” and
“single function of the trigger” are ambiguous, some lawmakers might seek to codify ATF’s
interpretation. Additionally, even if Congress agrees with ATF’s interpretation, codifying the bump-stock
ban through legislation would potentially preempt future lawsuits challenging the rulemaking process. In
the view of a majority of the en banc Fifth Circuit, “an act of Congress is required to prohibit bump
stocks.” Alternatively, lawmakers who disagree with ATF’s interpretation of existing law could seek to
supersede it through legislation excluding bump stocks from the statutory definition of “machinegun.”
Author Information
Dave S. Sidhu
Michael A. Foster
Legislative Attorney
Section Research Manager
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