Legal Sidebari

ATF’s Ability to Regulate “Bump Stocks”
Updated April 11, 2018
UPDATE: Following the publication of this Sidebar, the Justice Department’s Bureau of Alcohol,
Tobacco, Firearms, and Explosives (ATF) published a notice of proposed rulemaking declaring its
intention to clarify, through regulation, that “‘bump fire’ stocks, slide-fire devices, and devices with
certain similar characteristics (bump-stock-type devices) are ‘machineguns’” under the National
Firearms Act (NFA) and the Gun Control Act (GCA). In doing so, ATF proposes to interpret three terms
in the GCA and the NFA: (1) “single function of the trigger”; (2) “automatically”; and (3)
“machinegun.” Single function of the trigger will be defined as “single pull of the trigger.” Automatically
will 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.” And machinegun will include “a device that allows
semiautomatic firearms to shoot more than one shot with a single pull of the trigger by harnessing the
recoil energy of the semiautomatic firearm to which it is affixed so that the trigger resets and continues
firing without additional physical manipulation of the trigger by the shooter (commonly known as bump-
stock-type devices).” The public comment period closes June 27, 2018.

The original Sidebar post from March 22, 2018 providing background on the proposed rule is below.


Congressional interest in the legal framework for regulating “bump stock” devices abounded after
authorities discovered that the perpetrator of the October 2017 mass shooting in Las Vegas, Nevada, had
attached to his semiautomatic firearms an accessory that allowed his rifles to effectively mimic the firing
capabilities of a fully automatic weapon. (These firearm accessories are commonly called “bump-fire,”
“slide-fire,” or “bump-stock” devices, and more information on how they function can be found in this
CRS Insight by William J. Krouse.) One pertinent question involves the degree to which the Department
of Justice’s Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) may regulate, and potentially
proscribe, the sale and possession of such devices under existing law. The answer to this question largely
depends on whether a bump-stock device reasonably can be construed as falling under the federal
statutory definition of a “machinegun.”
In the months following the Las Vegas shooting, ATF, in an advance notice of proposed rulemaking,
sought public comment on “the nature and scope” of bump stock devices to help the agency determine
whether a bump stock is a “machinegun” as defined in the National Firearms Act of 1934 (NFA) and the
Gun Control Act of 1968 (GCA), as amended. The public comment period closed on January 25, 2018,
and six weeks later, on March 10, ATF submitted to the Office of Management and Budget (OMB) a
Congressional Research Service
https://crsreports.congress.gov
LSB10103
CRS INSIGHT
Prepared for Members and
Committees of Congress

---

Congressional Research Service
2
notice of a proposed regulation that would regulate bump-stock devices as machineguns. (If OMB
approves the draft proposed regulation, ATF may publish the proposed rule in the Federal Register for
public comment consistent with the procedures required by the Administrative Procedure Act. Following
the agency’s consideration of these comments, ATF will provide the draft final rule to OMB for review
before it may publish the rule as final.) The submission to OMB follows on the heels of President Trump's
directive to the Justice Department “to dedicate all available resources” to reviewing the comments
received and moving forward with rulemaking procedures with the goal of banning “all devices that turn
legal weapons into machineguns.” Also before the submission to OMB, Attorney General Sessions had
stated that Justice Department leadership “have believed for some time that we can, through regulatory
process, not allow the bump stock to convert a weapon from semiautomatic to fully automatic.” However,
some within ATF had reportedly believed the Bureau’s legal authority to regulate bump stocks, as they are
currently manufactured, was far from clear.
Statutory Framework: The NFA and, by cross-reference, the GCA, define a “machinegun” as “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.” Significantly, the definition
encompasses not only an automatic firearm itself, but also 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.” Devices falling under
these statutes’ definition of “machinegun” are subject to stringent regulation. For instance, the Firearm
Owners’ Protection Act of 1986 amended the GCA to prohibit the transfer and possession of a
machinegun subject to two exceptions. The prohibition does not apply to (1) the transfer to, or by, 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). The NFA governs the
lawful transfer and possession of machineguns. NFA-regulated machineguns must be registered with the
Attorney General, and the producer and transferor must pay a tax (subject to limited exceptions).
Regulatory Framework: Executive branch agencies have limited authority and may act only to the
extent authorized by Congress. Most executive branch agencies, including ATF, are authorized to
administer and interpret relevant existing laws through promulgating regulations. In doing so, an agency
must comply with statutorily required procedures and may not exceed its authority or act in an arbitrary
and capricious manner.
ATF’s consideration of whether bump stock devices categorically fall under the GCA and NFA’s
definition of “machinegun” turns on whether such devices may convert a firearm into one that shoots
“automatically ... by a single function of the trigger.” ATF previously has interpreted this phrase to cover
devices enabling a weapon to shoot “more than one shot, without manual reloading, by a single pull of the
trigger.”
In the past, ATF has not treated bump-stock devices as a homogenous category of firearm accessory. This
is likely because determining whether a firearm has been converted into a machinegun is a highly fact-
based inquiry, and depends on how the firearm, as modified, functions. Indeed, as noted in this CRS
Insight, ATF, in previous determinations as to whether a bump stock converts a semi-automatic firearm
into a machinegun, has reached different conclusions for different bump-stock devices based on how each
device uniquely functions. Now, ATF is assessing whether it has broad authority to regulate bump stocks
as a singular entity. Accordingly, the comments ATF receives about the functionality of bump stocks
currently on the market likely will inform ATF’s decision concerning whether a regulation banning bump
stocks is within the agency’s purview.
Considerations for Congress: As noted, ATF is presently determining whether its current legal authority
permits it to regulate the manufacture, sale, or possession of bump-stock devices. But the scope of

---

Congressional Research Service
3
ATF’s authority to regulate bump stock devices is a creature of statute, and Congress can act (within the
scope of constitutional parameters) to expand or curtail this authority. For example, if Congress wants
to give ATF clear authority to regulate bump stocks, it could do so by (1) expressly directing ATF to
initiate rulemaking to ban bump stocks within a certain timeline and/or (2) amending the definition of
“machinegun” under the NFA and GCA so that bump stocks necessarily will fall under that definition.
Alternatively, Congress, through its taxation powers (a constitutional basis for the NFA) and commerce
powers (the constitutional basis for the GCA) potentially could ban or otherwise regulate bump stocks
through independent legislation.

Author Information

Sarah Herman Peck

Legislative Attorney




Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff
to congressional committees and Members of Congress. It operates solely at the behest of and under the direction of
Congress. Information in a CRS Report should not be relied upon for purposes other than public understanding of
information that has been provided by CRS to Members of Congress in connection with CRS’s institutional role.
CRS Reports, as a work of the United States Government, are not subject to copyright protection in the United
States. Any CRS Report may be reproduced and distributed in its entirety without permission from CRS. However,
as a CRS Report may include copyrighted images or material from a third party, you may need to obtain the
permission of the copyright holder if you wish to copy or otherwise use copyrighted material.

LSB10103 · VERSION 5 · UPDATED

---