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															SUPREME COURT OF THE UNITED STATES

															_________________

															No. 22–976

															_________________

															MERRICK B. GARLAND, ATTORNEY GENERAL, et al.,
PETITIONERS v. MICHAEL CARGILL

															on writ of certiorari to the united states
court of appeals for the fifth circuit

															[June 14, 2024]

															Justice Thomas delivered the opinion of the
Court.

															Congress has long restricted access to
“ ‘machinegun[s],’ ” a category of firearms defined by
the ability to “shoot, automatically more than one shot
. . . by a single function of the trigger.” 26
U. S. C. §5845(b); see also 18 U. S. C.
§922( o ). Semiautomatic firearms, which require shooters to
reengage the trigger for every shot, are not machineguns. This case
asks whether a bump stock—an accessory for a semiautomatic rifle
that allows the shooter to rapidly reengage the trigger (and
therefore achieve a high rate of fire)—converts the rifle into a
“machinegun.” We hold that it does not and therefore affirm.

															I

															A

															Under the National Firearms Act of 1934, a
“machinegun” is “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.”
§5845(b). The statutory definition also includes “any part designed
and intended . . . for use in converting a weapon into a
machinegun.” Ibid. With a machinegun, a shooter can fire
multiple times, or even continuously, by engaging the trigger only
once. This capability distinguishes a machinegun from a
semiautomatic firearm. With a semiautomatic firearm, the shooter
can fire only one time by engaging the trigger. The shooter must
release and reengage the trigger to fire another shot. Machineguns
can ordinarily achieve higher rates of fire than semiautomatic
firearms because the shooter does not need to release and reengage
the trigger between shots.

															Shooters have devised techniques for firing
semiautomatic firearms at rates approaching those of some
machineguns. One technique is called bump firing. A shooter who
bump fires a rifle uses the firearm’s recoil to help rapidly
manipulate the trigger. The shooter allows the recoil from one shot
to push the whole firearm backward. As the rifle slides back and
away from the shooter’s stationary trigger finger, the trigger is
released and reset for the next shot. Simultaneously, the shooter
uses his nontrigger hand to maintain forward pressure on the
rifle’s front grip. The forward pressure counteracts the recoil and
causes the firearm (and thus the trigger) to move forward and
“bump” into the shooter’s trigger finger. This bump reengages the
trigger and causes another shot to fire, and so on.

															Bump firing is a balancing act. The shooter must
maintain enough forward pressure to ensure that he will bump the
trigger with sufficient force to engage it. But, if the shooter
applies too much forward pressure, the rifle will not slide back
far enough to allow the trigger to reset. The right balance
produces a reciprocating motion that permits the shooter to
repeatedly engage and release the trigger in rapid succession.

															Although bump firing does not require any
additional equipment, there are accessories designed to make the
technique easier. A “bump stock” is one such accessory.[ 1 ] It replaces a semiautomatic rifle’s
stock (the back part of the rifle that rests against the shooter’s
shoulder) with a plastic casing that allows every other part of the
rifle to slide back and forth. This casing helps manage the
back-and-forth motion required for bump firing. A bump stock also
has a ledge to keep the shooter’s trigger finger stationary. A bump
stock does not alter the basic mechanics of bump firing. As with
any semiautomatic firearm, the trigger still must be released and
reengaged to fire each additional shot.

															B

															The question in this case is whether a bump
stock transforms a semiautomatic rifle into a “machinegun,” as
defined by §5845(b). For many years, the Bureau of Alcohol,
Tobacco, Firearms and Explosives (ATF) took the position that
semiautomatic rifles equipped with bump stocks were not machineguns
under the statute. On more than 10 separate occasions over several
administrations, ATF consistently concluded that rifles equipped
with bump stocks cannot “automatically” fire more than one shot “by
a single function of the trigger.” See App. 16–68. In April 2017,
for example, ATF explained that a rifle equipped with a bump stock
does not “operat[e] automatically” because “forward pressure must
be applied with the support hand to the forward handguard.” Id., at 66. And, because the shooter slides the rifle
forward in the stock “to fire each shot, each succeeding shot
fir[es] with a single trigger function.” Id., at 67.

															ATF abruptly reversed course in response to a
mass shooting in Las Vegas, Nevada. In October 2017, a gunman fired
on a crowd attending an outdoor music festival in Las Vegas,
killing 58 people and wounding over 500 more. The gunman equipped
his weapons with bump stocks, which allowed him to fire hundreds of
rounds in a matter of minutes.

															This tragedy created tremendous political
pressure to outlaw bump stocks nationwide. Within days, Members of
Congress proposed bills to ban bump stocks and other devices
“designed . . . to accelerate the rate of fire of a
semiautomatic rifle.” S. 1916, 115th Cong., 1st Sess., §2 (2017);
see also H. R. 3947, 115th Cong., 1st Sess. (2017); H. R.
3999, 115th Cong., 1st Sess. (2017). None of these bills became
law. Similar proposals in the intervening years have also stalled.
See, e . g ., H. R. 396, 118th Cong., 1st Sess.
(2023); S. 1909, 118th Cong., 1st Sess. (2023); H. R.
5427, 117th Cong., 1st Sess. (2021).

															While the first wave of bills was pending, ATF
began considering whether to reinterpret §5845(b)’s definition of
“machinegun” to include bump stocks. It proposed a rule that would
amend its regulations to “clarify” that bump stocks are
machineguns. 83 Fed. Reg. 13442 (2018). ATF’s about-face drew
criticism from some observers, including those who agreed that bump
stocks should be banned. Senator Dianne Feinstein, for example,
warned that ATF lacked statutory authority to prohibit bump stocks,
explaining that the proposed regulation “ ‘hinge[d] on a
dubious analysis’ ” and that the “ ‘gun lobby and
manufacturers [would] have a field day with [ATF’s]
reasoning’ ” in court. Statement on Regulation To Ban Bump
Stocks (Mar. 23, 2018). She asserted that “ ‘legislation is
the only way to ban bump stocks.’ ” Ibid .

															ATF issued its final Rule in 2018. 83 Fed. Reg.
66514. The agency’s earlier regulations simply restated §5845(b)’s
statutory definition. Ibid. The final Rule amended those
regulations by adding the following language:

															“[T]he term ‘automatically’ as it modifies
‘shoots, is designed to shoot, or can be readily restored to
shoot,’ means 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; and ‘single function of
the trigger’ means a single pull of the trigger and analogous
motions. The term ‘machinegun’ includes a bump-stock-type device, i . e ., a device that 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.” Id ., at 66553–66554.

															The final Rule also repudiated ATF’s previous
guidance that bump stocks did not qualify as “machineguns” under
§5845(b). Id ., at 66530–66531. And, it ordered owners of
bump stocks to destroy them or surrender them to ATF within 90
days. Id ., at 66530. Bump-stock owners who failed to comply
would be subject to criminal prosecution. Id ., at 66525; see
also 18 U. S. C. §922( o )(1).

															C

															Michael Cargill surrendered two bump stocks to
ATF under protest. He then filed suit to challenge the final Rule,
asserting a claim under the Administrative Procedure Act. As
relevant, Cargill alleged that ATF lacked statutory authority to
promulgate the final Rule because bump stocks are not
“machinegun[s]” as defined in §5845(b). After a bench trial, the
District Court entered judgment for ATF. The court concluded that
“a bump stock fits the statutory definition of a
‘machinegun.’ ” Cargill v. Barr , 502
F. Supp. 3d 1163, 1194 (WD Tex. 2020).

															The Court of Appeals initially affirmed, 20
F. 4th 1004 (CA5 2021), but later reversed after rehearing en
banc, 57 F. 4th 447 (CA5 2023). A majority agreed, at a
minimum, that §5845(b) is ambiguous as to whether a semiautomatic
rifle equipped with a bump stock fits the statutory definition of a
machinegun. And, the majority concluded that the rule of lenity
required resolving that ambiguity in Cargill’s favor. Id .,
at 469; see also id ., at 450, n. An eight-judge plurality
determined that the statutory definition of “machinegun”
unambiguously excludes such weapons. A semiautomatic rifle equipped
with a bump stock, the plurality reasoned, fires only one shot
“each time the trigger ‘acts,’ ” id. , at 459, and so
does not fire “more than one shot . . . by a single
function of the trigger,” §5845(b). The plurality also concluded
that a bump stock does not enable a semiautomatic rifle to fire
more than one shot “automatically” because the shooter must
“maintain manual, forward pressure on the barrel.” Id ., at
463.

															We granted certiorari, 601 U. S. ___
(2023), to address a split among the Courts of Appeals regarding
whether bump stocks meet §5845(b)’s definition of
“machinegun.”[ 2 ] We now
affirm.

															II

															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.

															A

															A semiautomatic rifle equipped with a bump
stock does not fire more than one shot “by a single function of the
trigger.” With or without a bump stock, a shooter must release and
reset the trigger between every shot. And, any subsequent shot
fired after the trigger has been released and reset is the result
of a separate and distinct “function of the trigger.” All that a
bump stock does is accelerate the rate of fire by causing these
distinct “function[s]” of the trigger to occur in rapid
succession.

															As always, we start with the statutory text,
which refers to “a single function of the trigger.” The “function”
of an object is “the mode of action by which it fulfils its
purpose.” 4 Oxford English Dictionary 602 (1933); see also American
Heritage Dictionary 533 (1969) (“The natural or proper action for
which a . . . mechanism . . . is fitted or
employed”). And, a “trigger” is an apparatus, such as a “movable
catch or lever,” that “sets some force or mechanism in action.” 11
Oxford English Dictionary, at 357; see also American Heritage
Dictionary, at 1371 (“The lever pressed by the finger to discharge
a firearm” or “[a]ny similar device used to release or activate a
mechanism”); Webster’s New International Dictionary 2711 (2d ed.
1934) (“A piece, as a lever, connected with a catch or detent as a
means of releasing it; specif., Firearms , the part of a lock
moved by the finger to release the cock in firing”). The phrase
“function of the trigger” thus refers to the mode of action by
which the trigger activates the firing mechanism. For most
firearms, including the ones at issue here, the trigger is a curved
metal lever. On weapons with these standard trigger mechanisms, the
phrase “function of the trigger” means the physical trigger
movement required to shoot the firearm.

															No one disputes that a semiautomatic rifle
without a bump stock is not a machinegun because it fires only one
shot per “function of the trigger.” That is, engaging the trigger a
single time will cause the firing mechanism to discharge only one
shot. To understand why, it is helpful to consider the mechanics of
the firing cycle for a semiautomatic rifle. Because the statutory
definition is keyed to a “function of the trigger,” only the
trigger assembly is relevant for our purposes. Although trigger
assemblies for semiautomatic rifles vary, the basic mechanics are
generally the same. The following series of illustrations depicts
how the trigger assembly on an AR–15 style semiautomatic rifle
works.[ 3 ] In each illustration,
the front of the rifle ( i . e ., the barrel) would be
pointing to the left.

															We begin with an overview of the relevant
components:

															Figure 1.

															The trigger is a simple lever that moves
backward and forward. P. Sweeney, Gunsmithing the AR–15,
p. 131 (2016). The square point at the top left edge of the
trigger locks into a notch at the bottom of the hammer. P. Sweeney,
Gunsmithing: Rifles 269 (1999). The hammer is a spring-loaded part
that swings forward toward the barrel and strikes the firing pin,
causing a shot to fire. Ibid. The disconnector is the
component responsible for resetting the hammer to its original
position after a shot is fired. Ibid. We turn next to how these components
operate:

															Figure 2.

															When the shooter engages the trigger by moving
it backward (as indicated by the arrow), the square point of the
trigger pivots downward and out of the notch securing the hammer. Ibid. This movement releases the spring-loaded hammer,
allowing it to swing forward. Ibid. Figure 3.

															At the top of the hammer’s rotation, it strikes
the firing pin, causing the weapon to fire a single shot. See ibid. Figure 4.

															The firearm then ejects the spent cartridge from
the chamber and loads a new one in its place. D. Long, The Complete
AR–15/M16 Sourcebook 206 (2001). The mechanism that performs this
task swings the hammer backward at the same time. Ibid. Figure 5.

															As the hammer swings backward, it latches onto
the disconnector. Sweeney, Gunsmithing: Rifles, at 269. This
latching (circled above) prevents the hammer from swinging forward
again after a new cartridge is loaded into the chamber. Ibid. The disconnector will hold the hammer in that position
for as long as the shooter holds the trigger back, thus preventing
the firearm from firing another shot.[ 4 ] Ibid. Figure 6.

															Finally, when the shooter takes pressure off the
trigger and allows it to move forward (as indicated by the arrow),
the hammer slips off the disconnector just as the square point of
the trigger rises into the notch on the hammer (circled above). Ibid. The trigger mechanism is thereby reset to the original
position shown in Figure 1. A semiautomatic rifle must complete
this cycle for each shot fired.[ 5 ]

															ATF does not dispute that this complete process
is what constitutes a “single function of the trigger.” A shooter
may fire the weapon again after the trigger has reset, but only by
engaging the trigger a second time and thereby initiating a new
firing cycle. For each shot, the shooter must engage the trigger
and then release the trigger to allow it to reset. Any additional
shot fired after one cycle is the result of a separate and distinct
“function of the trigger.”

															Nothing changes when a semiautomatic rifle is
equipped with a bump stock. The firing cycle remains the same.
Between every shot, the shooter must release pressure from the
trigger and allow it to reset before reengaging the trigger for
another shot. A bump stock merely reduces the amount of time that
elapses between separate “functions” of the trigger. The bump stock
makes it easier for the shooter to move the firearm back toward his
shoulder and thereby release pressure from the trigger and reset
it. And, it helps the shooter press the trigger against his finger
very quickly thereafter. A bump stock does not convert a
semiautomatic rifle into a machinegun any more than a shooter with
a lightning-fast trigger finger does. Even with a bump stock, a
semiautomatic rifle will fire only one shot for every “function of
the trigger.” So, a bump stock cannot qualify as a machinegun under
§5845(b)’s definition.

															Although ATF agrees on a semiautomatic rifle’s
mechanics, it nevertheless insists that a bump stock allows a
semiautomatic rifle to fire multiple shots “by a single function of
the trigger.” ATF starts by interpreting the phrase “single
function of the trigger” to mean “a single pull of the trigger and
analogous motions.” 83 Fed. Reg. 66553. A shooter using a bump
stock, it asserts, must pull the trigger only one time to initiate
a bump-firing sequence of multiple shots. Id ., at 66554.
This initial trigger pull sets off a sequence—fire, recoil, bump,
fire—that allows the weapon to continue firing “without additional
physical manipulation of the trigger by the shooter.” Ibid. According to ATF, all the shooter must do is keep his trigger
finger stationary on the bump stock’s ledge and maintain constant
forward pressure on the front grip to continue firing. The dissent
offers similar reasoning. See post , at 7–9 (opinion of
Sotomayor, J.).

															This argument rests on the mistaken premise that
there is a difference between a shooter flexing his finger to pull
the trigger and a shooter pushing the firearm forward to bump the
trigger against his stationary finger. ATF and the dissent seek to
call the shooter’s initial trigger pull a “function of the trigger”
while ignoring the subsequent “bumps” of the shooter’s finger
against the trigger before every additional shot. But, §5845(b)
does not define a machinegun based on what type of human input
engages the trigger—whether it be a pull, bump, or something else.
Nor does it define a machinegun based on whether the shooter has
assistance engaging the trigger. The statutory definition instead
hinges on how many shots discharge when the shooter engages the
trigger. And, as we have explained, a semiautomatic rifle will fire
only one shot each time the shooter engages the trigger—with or
without a bump stock.[ 6 ] Supra , at 7–12.

															In any event, ATF’s argument cannot succeed on
its own terms. The final Rule defines “function of the trigger” to
include not only “a single pull of the trigger” but also any
“analogous motions.” 83 Fed. Reg. 66553. ATF concedes that one such
analogous motion that qualifies as a single function of the trigger
is “sliding the rifle forward” to bump the trigger. Brief for
Petitioners 22. But, if that is true, then every bump is a separate
“function of the trigger,” and semiautomatic rifles equipped with
bump stocks are therefore not machineguns. ATF resists the natural
implication of its reasoning, insisting that the bumping motion is
a “function of the trigger” only when it initiates, but not when it
continues, a firing sequence. But, Congress did not write a
statutory definition of “machinegun” keyed to when a firing
sequence begins and ends. Section 5845(b) asks only whether a
weapon fires more than one shot “by a single function of the
trigger.”

															Finally, the position that ATF and the dissent
endorse is logically inconsistent. They reason that a semiautomatic
rifle equipped with a bump stock fires more than one shot by a
single function of the trigger because a shooter “need only pull
the trigger and maintain forward pressure” to “activate continuous
fire.” Post , at 10; see also Brief for Petitioners 23. If
that is correct, however, then the same should be true for a
semiautomatic rifle without a bump stock. After all, as the
dissent and ATF themselves acknowledge, a shooter manually bump
firing a semiautomatic rifle can achieve continuous fire by holding
his trigger finger stationary and maintaining forward pressure with
his nontrigger hand. See post , at 5; 83 Fed. Reg. 66533.
Yet, they agree that a semiautomatic rifle without a bump stock
“fires only one shot each time the shooter pulls the trigger.” Post , at 4; see also 83 Fed. Reg. 66534. Their argument is
thus at odds with itself.

															We conclude that semiautomatic rifle equipped
with a bump stock is not a “machinegun” because it does not fire
more than one shot “by a single function of the trigger.”

															B

															A bump stock is not a “machinegun” for another
reason: Even if a semiautomatic rifle with a bump stock could fire
more than one shot “by a single function of the trigger,” it would
not do so “automatically.” Section 5845(b) asks whether a weapon
“shoots . . . automatically more than one shot
. . . by a single function of the trigger.” The statute
thus specifies the precise action that must “automatically” cause a
weapon to fire “more than one shot”—a “single function of the
trigger.” If something more than a “single function of the trigger”
is required to fire multiple shots, the weapon does not satisfy the
statutory definition. As Judge Henderson put it, the “statutory
definition of ‘machinegun’ does not include a firearm that shoots
more than one round ‘automatically’ by a single pull of the trigger AND THEN SOME .” Guedes v. Bureau of Alcohol,
Tobacco, Firearms and Explosives , 920 F.3d 1, 44 (CADC 2019)
(opinion concurring in part and dissenting in part).

															Firing multiple shots using a semiautomatic
rifle with a bump stock requires more than a single function of the
trigger. A shooter must also actively maintain just the right
amount of forward pressure on the rifle’s front grip with his
nontrigger hand. See supra , at 2–3. Too much forward
pressure and the rifle will not slide back far enough to release
and reset the trigger, preventing the rifle from firing another
shot. Too little pressure and the trigger will not bump the
shooter’s trigger finger with sufficient force to fire another
shot. Without this ongoing manual input, a semiautomatic rifle with
a bump stock will not fire multiple shots. Thus, firing multiple
shots requires engaging the trigger one time—and then
some.[ 7 ]

															ATF and the dissent counter that machineguns
also require continuous manual input from a shooter: He must both
engage the trigger and keep it pressed down to continue shooting.
In their view, there is no meaningful difference between holding
down the trigger of a traditional machinegun and maintaining
forward pressure on the front grip of a semiautomatic rifle with a
bump stock. This argument ignores that Congress defined a
machinegun by what happens “automatically” “by a single function of
the trigger.” Simply pressing and holding the trigger down on a
fully automatic rifle is not manual input in addition to a
trigger’s function—it is what causes the trigger to function in the
first place. By contrast, pushing forward on the front grip of a
semiautomatic rifle equipped with a bump stock is not part of
functioning the trigger. After all, pushing on the front grip will
not cause the weapon to fire unless the shooter also engages the
trigger with his other hand. Thus, while a fully automatic rifle
fires multiple rounds “automatically . . . by a single
function of the trigger,” a semiautomatic rifle equipped with a
bump stock can achieve the same result only by a single function of
the trigger and then some.

															Moreover, a semiautomatic rifle with a bump
stock is indistinguishable from another weapon that ATF concedes
cannot fire multiple shots “automatically”: the Ithaca Model 37
shotgun. The Model 37 allows the user to “slam fire”—that is, fire
multiple shots by holding down the trigger while operating the
shotgun’s pump action. Each pump ejects the spent cartridge and
loads a new one into the chamber. If the shooter is holding down
the trigger, the new cartridge will fire as soon as it is loaded.
According to ATF, the Model 37 fires more than one shot by a single
function of the trigger, but it does not do so “automatically”
because the shooter must manually operate the pump action with his
nontrigger hand. See 83 Fed. Reg. 66534. That logic mandates the
same result here. Maintaining the proper amount of forward pressure
on the front grip of a bump-stock equipped rifle is no less
additional input than is operating the pump action on the Model
37.[ 8 ]

															ATF responds that a shooter is less physically
involved with operating a bump-stock equipped rifle than operating
the Model 37’s pump action. Once the shooter pulls the rifle’s
trigger a single time, the bump stock “harnesses the firearm’s
recoil energy in a continuous back-and-forth cycle that allows the
shooter to attain continuous firing.” Id., at 66519. But,
even if one aspect of a weapon’s operation could be seen as
“automatic,” that would not mean the weapon “shoots . . .
automatically more than one shot . . . by a single
function of the trigger .” §5845(b) (emphasis added). After all,
many weapons have some “automatic” features. For example,
semiautomatic rifles eject the spent cartridge from the firearm’s
chamber and load a new one in its place without any input from the
shooter. See supra , at 10. A semiautomatic rifle is
therefore “automatic” in the general sense that it performs some
operations that would otherwise need to be completed by hand. But,
as all agree, a semiautomatic rifle cannot fire more than one shot
“automatically . . . by a single function of the trigger”
because the shooter must do more than simply engage the trigger one
time. The same is true of a semiautomatic rifle equipped with a
bump stock.

															Thus, even if a semiautomatic rifle could fire
more than one shot by a single function of the trigger, it would
not do so “automatically.”

															C

															Abandoning the text, ATF and the dissent
attempt to shore up their position by relying on the presumption
against ineffectiveness. That presumption weighs against
interpretations of a statute that would “rende[r] the law in a
great measure nugatory, and enable offenders to elude its
provisions in the most easy manner.” The Emily , 9 Wheat.
381, 389 (1824). It is a modest corollary to the commonsense
proposition “that Congress presumably does not enact useless laws.” United States v. Castleman , 572
U.S. 157 , 178 (2014) (Scalia, J., concurring in part and
concurring in judgment).

															In ATF’s view, Congress “restricted machineguns
because they eliminate the manual movements that a shooter would
otherwise need to make in order to fire continuously” at a high
rate of fire, as bump stocks do. Brief for Petitioners 40. So, ATF
reasons, concluding that bump stocks are lawful “simply because the
[trigger] moves back and forth . . . would exalt artifice
above reality and enable evasion of the federal machinegun ban.” Id ., at 41–42 (internal quotation marks omitted). The
dissent endorses a similar view. See post , at 14–17.

															The presumption against ineffectiveness cannot
do the work that ATF and the dissent ask of it. A law is not
useless merely because it draws a line more narrowly than one of
its conceivable statutory purposes might suggest. Interpreting
§5845(b) to exclude semiautomatic rifles equipped with bump stocks
comes nowhere close to making it useless. Under our reading,
§5845(b) still regulates all traditional machineguns. The fact that
it does not capture other weapons capable of a high rate of fire
plainly does not render the law useless. Moreover, it is difficult
to understand how ATF can plausibly argue otherwise, given that its
consistent position for almost a decade in numerous separate
decisions was that §5845(b) does not capture semiautomatic rifles
equipped with bump stocks. See App. 16–68. Curiously, the dissent
relegates ATF’s about-face to a footnote, instead pointing to its
classification of other devices. See post , at 14–17, and
n. 6.

															The dissent’s additional argument for applying
the presumption against ineffectiveness fails on its own terms. To
argue that our interpretation makes §5845(b) “far less effective,”
the dissent highlights that a shooter with a bump-stock-equipped
rifle can achieve a rate of fire that rivals traditional
machineguns. Post , at 16. But, the dissent elsewhere
acknowledges that a shooter can do the same with an unmodified semiautomatic rifle using the manual bump-firing
technique. See post , at 5. The dissent thus fails to prove
that our reading makes §5845(b) “far less effective,” much less
ineffective (as is required to invoke the presumption). In any
event, Congress could have linked the definition of “machinegun” to
a weapon’s rate of fire, as the dissent would prefer. But, it
instead enacted a statute that turns on whether a weapon can fire
more than one shot “automatically . . . by a single
function of the trigger.” §5845(b). And, “it is never our job to
rewrite . . . statutory text under the banner of
speculation about what Congress might have done.” Henson v. Santander Consumer USA Inc. , 582 U.S. 79, 89
(2017).[ 9 ]

															III

															For the foregoing reasons, we affirm the
judgment of the Court of Appeals.

															It is so ordered. Notes 1 Some bump stocks (called
mechanical bump stocks) rely on an internal spring, rather than
forward pressure from the shooter’s nontrigger hand, to force the
rifle and trigger forward after recoil. These devices are not at
issue in this case. 2 See, e . g ., Hardin v. Bureau of Alcohol, Tobacco, Firearms and
Explosives , 65 F. 4th 895 (CA6 2023); Guedes v. Bureau of Alcohol, Tobacco, Firearms and Explosives , 45
F. 4th 306 (CADC 2022); Aposhian v. Barr , 958
F.3d 969 (CA10 2020). 3 These illustrations are
found in the Brief for FPC Action Foundation as Amicus
Curiae 14–15. 4 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. P. Sweeney, 1 The Gun Digest Book of
the AR–15, p. 38 (2005). 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. See ATF
Ruling 81–4. 5 An animated graphic that
displays the relevant movements is available at
https://www.supremecourt.gov/media/images/AR-15.gif. 6 The dissent says that we
“resis[t]” the “ordinary understanding of the term ‘function of the
trigger’ with two technical arguments.” Post , at 10. But,
the arguments it refers to explain why, even assuming a
semiautomatic rifle equipped with a bump stock could fire more than
one shot by a single function of the trigger, it could not do so
“automatically.” See infra , at 14–17. Those arguments have
nothing to do with our explanation of what a “single function of
the trigger” means. Ibid. 7 The dissent seemingly
concedes this point, repeatedly recognizing that the shooter must
both pull the trigger and maintain forward pressure on the
front grip. See, e . g ., post , at 6 (“[A] single
pull of the trigger provides continuous fire as long as the shooter
maintains forward pressure on the gun”); ibid . (“A
bump-stock-equipped semiautomatic rifle is a machinegun because
. . . a shooter can . . . fire continuous shots
without any human input beyond maintaining forward pressure”); post , at 10 (“[A] shooter of a bump-stock-equipped AR–15
need only pull the trigger and maintain forward pressure”); post , at 13 (“After a shooter pulls the trigger, if he
maintains continuous forward pressure on the gun, the bump stock
harnesses the recoil to move the curved lever back and forth
against his finger”). 8 The dissent attempts to
undermine this analogy by pointing out that a Model 37 requires
manual reloading and therefore cannot qualify as a machinegun under
§5845(b). Post , at 12–13, n. 5. But, that is beside the
point. As ATF itself agrees, the Model 37 is not a machinegun for
another, independent reason: It cannot “automatically” fire more
than one shot by a single function of the trigger. See Brief for
Petitioners 38. And, as explained, the reasons why a Model 37
cannot do so apply with equal force to semiautomatic rifles
equipped with bump stocks. 9 The dissent concludes by
claiming that our interpretation of §5845(b) “renders Congress’s
clear intent readily evadable.” Post , at 17. And, it
highlights that “[e]very Member of the majority has previously
emphasized that the best way to respect congressional intent is to
adhere to the ordinary understanding of the terms Congress uses.” Ibid . But, “[w]hen Congress takes the trouble to define the
terms it uses, a court must respect its definitions as virtually
conclusive. . . . This Court will not deviate from an
express statutory definition merely because it varies from the
term’s ordinary meaning.” Department of Agriculture Rural
Development Rural Housing Service v. Kirtz , 601 U.S. 42,
59 (2024) (internal quotation marks and alteration omitted)
(unanimous opinion). SUPREME COURT OF THE UNITED STATES

															_________________

															No. 22–976

															_________________

															MERRICK B. GARLAND, ATTORNEY GENERAL, et al.,
PETITIONERS v. MICHAEL CARGILL

															on writ of certiorari to the united states
court of appeals for the fifth circuit

															[June 14, 2024]

															Justice Alito, concurring.

															I join the opinion of the Court because there is
simply no other way to read the statutory language. There can be
little doubt that the Congress that enacted 26 U. S. C.
§5845(b) would not have seen any material difference between a
machinegun and a semiautomatic rifle equipped with a bump stock.
But the statutory text is clear, and we must follow it.

															The horrible shooting spree in Las Vegas in 2017
did not change the statutory text or its meaning. That event
demonstrated that a semiautomatic rifle with a bump stock can have
the same lethal effect as a machinegun, and it thus strengthened
the case for amending §5845(b). But an event that highlights the
need to amend a law does not itself change the law’s meaning.

															There is a simple remedy for the disparate
treatment of bump stocks and machineguns. Congress can amend the
law—and perhaps would have done so already if ATF had stuck with
its earlier interpretation. Now that the situation is clear,
Congress can act. SUPREME COURT OF THE UNITED STATES

															_________________

															No. 22–976

															_________________

															MERRICK B. GARLAND, ATTORNEY GENERAL, et al.,
PETITIONERS v. MICHAEL CARGILL

															on writ of certiorari to the united states
court of appeals for the fifth circuit

															[June 14, 2024]

															Justice Sotomayor, with whom Justice Kagan and
Justice Jackson join, dissenting.

															On October 1, 2017, a shooter opened fire from a
hotel room overlooking an outdoor concert in Las Vegas, Nevada, in
what would become the deadliest mass shooting in U. S.
history. Within a matter of minutes, using several hundred rounds
of ammunition, the shooter killed 58 people and wounded over 500.
He did so by affixing bump stocks to commonly available,
semiautomatic rifles. These simple devices harness a rifle’s recoil
energy to slide the rifle back and forth and repeatedly “bump” the
shooter’s stationary trigger finger, creating rapid fire. All the
shooter had to do was pull the trigger and press the gun forward.
The bump stock did the rest.

															Congress has sharply restricted civilian
ownership of machineguns since 1934. Federal law defines a
“machinegun” as a weapon that can shoot “automatically more than
one shot, without manual reloading, by a single function of the
trigger.” 26 U. S. C. §5845(b). Shortly after the Las
Vegas massacre, the Trump administration, with widespread
bipartisan support, banned bump stocks as machineguns under the
statute.

															Today, the Court puts bump stocks back in
civilian hands. To do so, it casts aside Congress’s definition of
“machinegun” and seizes upon one that is inconsistent with the
ordinary meaning of the statutory text and unsupported by context
or purpose. When I see a bird that walks like a duck, swims like a
duck, and quacks like a duck, I call that bird a duck. A
bump-stock-equipped semiautomatic rifle fires “automatically more
than one shot, without manual reloading, by a single function of
the trigger.” §5845(b). Because I, like Congress, call that a
machinegun, I respectfully dissent.

															I

															A

															Machineguns were originally developed in the
19th century as weapons of war. See J. Ellis, The Social History of
the Machine Gun 21–45 (1986) (Ellis). Smaller and lighter
submachine guns were not commercially available until the 1920s.
See Brief for Patrick J. Charles as Amicus Curiae 5 (Charles
Brief ). Although these weapons were originally marketed to
law enforcement, they inevitably made it into the hands of
gangsters. See id ., at 8–9; Ellis 149–165. Gangsters like Al
Capone used machineguns to rob banks, ambush the police, and murder
rivals. See Ellis 153–154, 157–158. Newspaper headlines across the
country flashed “ ‘Gangsters Use Machine Guns,’ ”
“ ‘Machine Gun Used in Bank Hold-Up,’ ” and
“ ‘Machine Gun Thugs Kill Postal Employee.’ ” Charles
Brief 9.

															Congress responded in 1934 by sharply
restricting civilian ownership of machineguns. See National
Firearms Act of 1934, §§3–6, 48Stat. 1236, 1237–1238. The Senate
Report explaining the 1934 Act emphasized that the “gangster as a
law violator must be deprived of his most dangerous weapon, the
machine gun.” S. Rep. No. 1444, 73d Cong., 2d Sess., 1–2.
“[W]hile there is justification for permitting the citizen to keep
a pistol or revolver for his own
protection . . . , there is no reason why
anyone except a law officer should have a machine gun.” Id .,
at 2.

															These early machineguns allowed a shooter to
fire in a variety of ways. Some would fire continuously with a
single pull of the trigger or push of a button. See Charles Brief
7, and n. 12 (noting that a Browning M1918 rifle fired eight
rounds “ ‘in a second with one pull of the trigger’ ”);
see also Brief for Petitioners 22 (noting that a Browning M2 fired
with a push of the thumb). Others, such as the famous Thompson
Submachine Gun Caliber .45, or “Tommy Gun,” would fire continuously
only so long as the shooter maintained backward pressure on the
trigger; a shooter could still fire single shots by pulling and
releasing the trigger each time. See Test of Thompson Submachine
Gun, 69 Army and Navy Register 355 (Apr. 9, 1921) (noting that the
shooter of a Tommy Gun “can fire the contents of the magazine with
a single prolonged pull or fire a single shot by merely releasing
the trigger”). The internal mechanisms of automatic-fire weapons
also varied enormously, with many (such as the Tommy Gun) relying
principally on the recoil energy produced by each bullet’s
discharge to effectuate automatic fire. See, e . g .,
War Dept., Basic Field Manual: Thompson Submachine Gun, Caliber
.45, M1928A1, p. 1 (1941) (“The Thompson submachine gun
. . . is an air-cooled, recoil-operated, magazine-fed
weapon”); W. Smith, Small Arms of the World: The Basic Manual of
Military Small Arms 165 (1955) (describing Tommy guns as “recoil
operated weapons on the elementary blowback principle”).

															To account for these differences, Congress
adopted a definition of “machinegun” that captured “any weapon
which shoots, or is designed to shoot, automatically
. . . more than one shot, without manual reloading, by a
single function of the trigger.” National Firearms Act, 48Stat.
1236. That essential definition still governs today. See 26
U. S. C. §5845(b).[ 1 ]

															B

															The archetypal modern “machinegun” is the
military’s standard-issue M16 assault rifle. With an M16 in
automatic mode, the shooter pulls the trigger once to achieve a
fire rate of 700 to 950 rounds per minute. See Dept. of Defense,
Defense Logistics Agency, Small Arms, https://www.
dla.mil/Disposition-Services/Offers/ Law- Enforcement /
Weapons/. An internal mechanism automates the M16’s continuous
fire, so that all the shooter has to do is keep backward pressure
on the trigger. See Brief for Giffords Law Center to Prevent Gun
Violence et al. as Amici Curiae 9–11 (Giffords
Brief ) (discussing internal firing mechanism of M16). If the
shooter stops putting pressure on the trigger, the gun stops
firing.

															Semiautomatic weapons are not “machineguns”
under the statute. Take, for instance, an AR–15-style semiautomatic
assault rifle. To rapidly fire an AR–15, a shooter must rapidly
pull the trigger himself. It is “semi” automatic because, although
the rifle automatically loads a new cartridge into the chamber
after it is fired, it fires only one shot each time the shooter
pulls the trigger. See 18 U. S. C. §921(a)(29) (2018 ed.,
Supp. IV).

															To fire an M16 or AR–15 rifle, a person
typically holds the “grip” next to the trigger with his firing
hand. He stabilizes the weapon with his other hand on its barrel or
“front grip.” He then raises the weapon so that the butt, or
“stock,” of the gun rests against his shoulder, lines up the sights
to look down the gun, and squeezes the trigger. See Dept. of the
Army, Field Manual 23–9, Rifle Marksmanship M16A1, M16A2/3, M16A4,
and M4 Carbine, Ch. 4, Section III, p. 4-22 (Sept. 13, 2006)
(M16 Field Manual). A regular person with an AR–15 can achieve a
fire rate of around 60 rounds per minute, with one pull of the
trigger per second. Tr. of Oral Arg. 39. A professional sport
shooter can use the AR–15 to fire at a rate of up to 180 rounds per
minute, pulling the trigger three times per second. Giffords Brief
14.

															A shooter can also manually “bump” an AR–15 to
increase the rate of fire by using a belt loop or rubber band to
hold his trigger finger in place and harness the recoil from the
first shot to fire the rifle continuously. See 83 Fed. Reg.
66532–66533 (2018). To use a belt loop, he must hold the rifle low
against his hip, put his finger in the trigger guard, and then loop
his finger through a belt loop on his pants to lock the finger in
place. See id ., at 66533. With his other hand, he then
pushes the rifle forward until his stationary finger engages the
trigger to fire the first shot. See ibid. The recoil from
that shot pushes the rifle violently backward. See ibid. If
the shooter keeps pressing the rifle forward against the finger in
his belt loop, the repeated backward jump of the recoil combined
with his forward pressure allows the rifle to fire continuously.
See ibid. A shooter using this method, however, cannot shoot
very precisely. He has neither the advantage of the sights to line
up his shot, nor his shoulder to stabilize the recoil. A shooter
can also use a rubber band or zip tie to tie a finger close to the
trigger. See id ., at 66532. If the shooter is strong and
skilled enough physically to control the distance and direction of
the rifle’s significant recoil, the rifle will fire
continuously.

															A bump stock automates and stabilizes the bump
firing process. It replaces a rifle’s standard stock, which is the
part held against the shoulder. See id ., at 66516. A bump
stock, unlike a standard stock, allows the rifle’s upper assembly
to slide back and forth in the stock. See ibid. It also
typically includes a finger rest on which the shooter can place his
finger while shooting, and a “receiver module” that guides and
regulates the weapon’s recoil. Ibid. To fire a semiautomatic
rifle equipped with a bump stock, the shooter either pulls the
trigger, see ibid. , or slides the gun forward in the bump
stock, which presses the trigger into his trigger finger, Cargill v. Barr , 502 F. Supp. 3d 1163, 1175 (WD
Tex. 2020). As long as the shooter keeps his trigger finger on the
finger rest and maintains constant forward pressure on the rifle’s
barrel or front grip, the weapon will fire continuously. See 83
Fed. Reg. 66516. A rifle equipped with a bump stock can fire at a
rate between 400 and 800 rounds per minute. Tr. of Oral Arg.
40.

															II

															A machinegun does not fire itself. The
important question under the statute is how a person can fire it. A
weapon is a “machinegun” when a shooter can (1) “by a single
function of the trigger,” (2) shoot “automatically more than one
shot, without manually reloading.” 26 U. S. C. §5845(b).
The plain language of that definition refers most obviously to a
rifle like an M16, where a single pull of the trigger provides
continuous fire as long as the shooter maintains backward pressure
on the trigger. The definition of “machinegun” also includes “any
part designed and intended . . . for use in converting a
weapon into a machinegun.” Ibid. That language naturally
covers devices like bump stocks, which “conver[t]” semiautomatic
rifles so that a single pull of the trigger provides continuous
fire as long as the shooter maintains forward pressure on the
gun.

															This is not a hard case. All of the textual
evidence points to the same interpretation. A bump-stock-equipped
semiautomatic rifle is a machinegun because (1) with a single pull
of the trigger, a shooter can (2) fire continuous shots without any
human input beyond maintaining forward pressure. 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. See ante, at
8–11, and n. 5. Then, shifting focus from the internal
mechanism of the gun to the perspective of the shooter, the
majority holds that continuous forward pressure is too much human
input for bump-stock-enabled continuous fire to be “automatic.” See ante, at 14–17.

															The majority’s reading flies in the face of this
Court’s standard tools of statutory interpretation. By casting
aside the statute’s ordinary meaning both at the time of its
enactment and today, the majority eviscerates Congress’s regulation
of machineguns and enables gun users and manufacturers to
circumvent federal law.

															A

															Start with the phrase “single function of the
trigger.” All the tools of statutory interpretation, including
dictionary definitions, evidence of contemporaneous usage, and this
Court’s prior interpretation, point to that phrase meaning the
initiation of the firing sequence by an act of the shooter, whether
via a pull, push, or switch of the firing mechanism. The majority
nevertheless interprets “function of the trigger” as “the mode of
action by which the trigger activates the firing mechanism.” Ante, at 7. Because in a bump-stock-equipped semiautomatic
rifle, the trigger’s internal mechanism must reset each time a
weapon fires, the majority reads each reset as a new “function.”
That reading fixates on a firearm’s internal mechanics while
ignoring the human act on the trigger referenced by the
statute.

															Consider the relevant dictionary definitions. In
1934, when Congress passed the National Firearms Act, “function”
meant “the mode of action by which [something] fulfils its
purpose.” 4 Oxford English Dictionary 602 (1933). A “trigger” meant
the “movable catch or lever” that “sets some force or mechanism in
action.” 11 id ., at 357. The majority agrees with those
definitions. Ante, at 7. It errs, however, by maintaining a
myopic focus on a trigger’s mechanics rather than on how a shooter
uses a trigger to initiate fire. Ibid. Nothing about those definitions suggests that
“function of the trigger” means the mechanism by which the trigger
resets mechanically to fire a second shot. See ante , at 8–11
(explaining the interior mechanics of an AR–15 trigger mechanism),
as opposed to the process that a pull of the trigger on a
bump-stock-equipped semiautomatic rifle sets in motion. The most
important “function” of a “trigger” is what it enables a shooter to
do; what “force or mechanism” it sets “in action.” 11 Oxford
English Dictionary, at 357. A “single function of the trigger” more
naturally means a single initiation of the firing sequence.
Regardless of what is happening in the internal mechanics of a
firearm, if a shooter must activate the trigger only a single time
to initiate a firing sequence that will shoot “automatically more
than one shot,” that firearm is a “machinegun.” §5845(b).

															Evidence of contemporaneous usage overwhelmingly
supports that interpretation. The term “ ‘function of the
trigger’ ” was proposed by the president of the National Rifle
Association (NRA) during a hearing on the National Firearms Act
before the House. See National Firearms Act: Hearings on H. R.
9066 before the House Committee on Ways and Means, 73d Cong., 2d
Sess., 38–40 (1934). He understood the “distinguishing feature of a
machine gun [to be] that by a single pull of the trigger the gun
continues to fire.” Id ., at 40. He emphasized that a firearm
“which is capable of firing more than one shot by a single pull of
the trigger, a single function of the trigger, is properly regarded
. . . as a machine gun.” Ibid. Distinguishing a
machinegun from a pistol, the NRA president emphasized that for a
pistol “[y]ou must release the trigger and pull it again for the
second shot to be fired.” Id ., at 41. He did not say “the
hammer slips off the disconnector just as the square point of the
trigger rises into the notch on the hammer . . . thereby
reset[ting the trigger mechanism] to the original position.” Ante, at 11. He instead emphasized the action of the
shooter, who must repeatedly activate the trigger for each shot.
Predictably, the House and Senate Reports reflect the same
understanding of the phrase. See H. R. Rep. No. 1780, 73d
Cong., 2d Sess., 2 (1934) (reporting that the statute “contains the
usual definition of machine gun as a weapon designed to shoot more
than one shot without reloading and by a single pull of the
trigger”); S. Rep. No. 1444, 73d Cong., 2d Sess., 2 (1934)
(same).

															The majority cannot disregard these statements
as evidence of legislative purpose.[ 2 ] They are, along with contemporaneous dictionary
definitions, some of the best evidence of contemporaneous
understanding. Cf. McDonald v. Chicago , 561 U.S.
742 , 828 (2010) (Thomas, J., concurring in part and concurring
in judgment) (“Statements by legislators can assist . . .
to the extent they demonstrate the manner in which the public used
or understood a particular word or phrase”). Indeed, at oral
argument, when asked what evidence there was “that as of 1934, the
ordinary understanding of the phrase ‘function of the trigger’
referred to the mechanics of the gun rather than . . .
the shooter’s motion,” respondent’s lawyer could not point to a
single piece of evidence that supports the majority’s reading. Tr.
of Oral Arg. 98; see id ., at 98–101. He even agreed that
Congress used the word “function” to ensure that the statute
covered a wide variety of trigger mechanisms, including both push
and pull triggers. Id ., at 101–102. In short, the majority
disregards the unrefuted evidence of the text’s ordinary and
contemporaneous meaning, substituting instead its own understanding
of the internal mechanics of an AR–15 without looking at the
actions of the shooter.

															This Court itself has also previously read the
definition of “machinegun” in this exact statute to refer to the
action of the shooter rather than the firing mechanism. In Staples v. United States , 511
U.S. 600 (1994), the Court noted that “a weapon that fires
repeatedly with a single pull of the trigger ” is a
machinegun, as opposed to “a weapon that fires only one shot with
each pull of the trigger,” which is (at most) a semiautomatic
firearm. Id ., at 602, n. 1 (emphasis added). A “pull”
of the trigger necessarily requires human input.

															When a shooter initiates the firing sequence on
a bump-stock-equipped semiautomatic rifle, he does so with “a
single function of the trigger” under that term’s ordinary meaning.
Just as the shooter of an M16 need only pull the trigger and
maintain backward pressure (on the trigger), a shooter of a
bump-stock-equipped AR–15 need only pull the trigger and maintain
forward pressure (on the gun). Both shooters pull the trigger only
once to fire multiple shots. The only difference is that for an
M16, the shooter’s backward pressure makes the rifle fire
continuously because of an internal mechanism: The curved lever of
the trigger does not move. In a bump-stock-equipped AR–15, the
mechanism for continuous fire is external: The shooter’s forward
pressure moves the curved lever back and forth against his
stationary trigger finger. Both rifles require only one initial
action (that is, one “single function of the trigger”) from the
shooter combined with continuous pressure to activate continuous
fire.[ 3 ]

															The majority resists this ordinary understanding
of the term “function of the trigger” with two technical
arguments.[ 4 ] First, it
attempts to contrast the action required to fire an M16 from that
required to fire a bump-stock-equipped AR–15. The majority argues
that “holding the trigger down on a fully automatic rifle is not
manual input in addition to a trigger’s function—it is what causes
the trigger to function in the first place” whereas “pushing on the
front grip [of a bump-stock equipped semiautomatic rifle] will not
cause the weapon to fire unless the shooter also engages the
trigger with his other hand.” Ante, at 16. The shooter of a
bump-stock-equipped AR–15, however, need not “pull” the trigger to
fire. Instead, he need only place a finger on the finger rest and
push forward on the front grip or barrel with his other hand.
Instead of pulling the trigger, the forward motion pushes the bump
stock into his finger.

															Second, the majority tries to cabin “single
function of the trigger” to a single mechanism for activating
continuous fire. See ante, at 14–15. A shooter can fire a
bump-stock-equipped semiautomatic rifle in two ways. First, he can
choose to fire single shots via distinct pulls of the trigger
without exerting any additional pressure. Second, he can fire
continuously via maintaining constant forward pressure on the
barrel or front grip. The majority holds that the forward pressure
cannot constitute a “single function of the trigger” because a
shooter can also fire single shots by pulling the trigger. That
logic, however, would also exclude a Tommy Gun and an M16, the
paradigmatic examples of regulated machineguns in 1934 and today.
Both weapons can fire either automatically or semiautomatically. A
shooter using a Tommy Gun in automatic mode could choose to fire
single shots with distinct pulls of the trigger, or continuous
shots by maintaining constant backward pressure on the trigger. See supra , at 3. An M16 user can toggle the weapon from
semiautomatic mode, which allows only one shot per pull of the
trigger, to automatic mode, which enables continuous fire. See M16
Field Manual, Section III, p. 4-8. In 1934 as now, there is no
commonsense difference between a firearm where a shooter must hold
down a trigger or flip a switch to initiate rapid fire and one
where a shooter must push on the front grip or barrel to do the
same.

															The majority’s logic simply does not overcome
the overwhelming textual and contextual evidence that “single
function of the trigger” means a single action by the shooter to
initiate a firing sequence, including pulling a trigger and pushing
forward on a bump-stock-equipped semiautomatic rifle.

															B

															Next, consider what makes a machinegun
“automatic.” A bump-stock-equipped semiautomatic rifle is a
“machinegun” because with a “single function of the trigger” it
“shoot[s], automatically more than one shot, without manual
reloading.” §5845(b). Put simply, the bump stock automates the
process of firing more than one shot.

															Before automatic weapons, a person who wanted to
fire multiple shots from a firearm had to do two things after
pulling the trigger the first time: (1) he had to reload the gun;
and (2) he had to pull the trigger again. A semiautomatic weapon
like an AR–15 already automates the first process. The bump stock
automates the second.[ 5 ] In a
fully automatic rifle like an M16, that automation is internal.
After a shooter pulls the trigger, if he maintains continuous
backward pressure on the trigger, the curved lever itself will not
move. Instead, an internal mechanism allows continuous fire. On a
bump-stock-equipped semiautomatic rifle, the automation is
external. After a shooter pulls the trigger, if he maintains
continuous forward pressure on the gun, the bump stock harnesses
the recoil to move the curved lever back and forth against his
finger. That external automated motion creates continuous fire.

															When a shooter “bump” fires a semiautomatic
weapon without a bump stock, he must control several things using
his own strength and skill: (1) the backward recoil of each
shot, including both the direction in which the rifle moves and how
far it moves when recoiling; (2) the trigger finger, by
maintaining a stationary position with a loose enough hold on the
trigger that the rapidly moving gun will hit his finger each time;
and (3) the forward motion of the rifle after it recoils
backward. A bump stock automates those processes. The replacement
stock controls the direction and distance of the recoil, and the
finger rest obviates the need to maintain a stationary finger
position. All a shooter must do is rest his finger and press
forward on the front grip or barrel for the rifle to fire
continuously.

															The majority nevertheless concludes that a
bump-stock-equipped semiautomatic rifle requires too much human
input to fire “automatic[ally]” because it requires the “proper
amount of forward pressure on the front grip” to maintain
continuous fire. Ante, at 16. “Automati[c],” however, does
not mean zero human input. An M16 requires the shooter to exert the
“proper amount of [backward] pressure on the” trigger to maintain
continuous fire. Ibid. So, too, a machinegun that requires a
user to hold down a button. Makers of automatic weapons may require
continuous human input for safety purposes; an accidental trigger
pull that activates rapid fire is less harmful if it does not
require affirmative human action to stop. Requiring continuous
pressure for continuous fire, however, does not prevent a firearm
from “shoot[ing], automatically more than one shot.” §5845(b).

															C

															This Court has repeatedly avoided
interpretations of a statute that would facilitate its ready
“evasion” or “enable offenders to elude its provisions in the most
easy manner.” The Emily , 9 Wheat. 381, 389–390 (1824); see
also Abramski v. United States , 573 U.S.
169 , 181–182, 185 (2014) (declining to read a gun statute in a
way that would permit ready “evasion,” “defeat the point” of the
law, or “easily bypass the scheme”). Justice Scalia called this
interpretive principle the “presumption against ineffectiveness.”
A. Scalia & B. Garner, Reading Law: The Interpretation of Legal
Texts 63 (2012). The majority arrogates Congress’s policymaking
role to itself by allowing bump-stock users to circumvent
Congress’s ban on weapons that shoot rapidly via a single action of
the shooter.

															“The presumption against ineffectiveness ensures
that a text’s manifest purpose is furthered, not hindered.” Ibid. Before machineguns, a shooter could fire a gun only as
fast as his finger could pull the trigger. Congress sought to
restrict the civilian use of machineguns because they eliminated
the need for a person rapidly to pull the trigger himself to fire
continuously. A bump stock serves that function. Even a skilled
sport shooter can fire an AR–15 at a rate of only 180 rounds per
minute by rapidly pulling the trigger. Anyone shooting a
bump-stock-equipped AR–15 can fire at a rate between 400 and 800
rounds per minute with a single pull of the trigger.

															Moreover, bump stocks are not the only devices
that transform semiautomatic rifles into weapons capable of rapid
fire with a single function of the trigger. Recognizing the
creativity of gun owners and manufacturers, Congress wrote a
statute “loaded with anticircumvention devices.” Tr. of Oral Arg.
68. The definition of “machinegun” captures “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.” §5845(b). Not “more than four,
five, or six shots,” not “single pull” or “single push” of the
trigger.” Following that definition, the Bureau of Alcohol,
Tobacco, Firearms and Explosives (ATF) has reasonably classified
many transformative devices other than bump stocks as
“machinegun[s].”[ 6 ] For
instance, ATF has long classified “forced reset triggers” as
machineguns. See Brief for Petitioners 28. A forced reset trigger
includes a device that forces the trigger back downward after the
shooter’s initial pull, repeatedly pushing the curved lever against
the shooter’s stationary trigger finger. See ibid. To a
shooter, a semiautomatic rifle equipped with a forced reset trigger
feels much like an M16. He must pull the trigger only once and then
maintain pressure to achieve continuous fire. See ibid. Gun owners themselves also have built motorized
devices that will repeatedly pull a semiautomatic firearm’s curved
lever to enable continuous fire. ATF has classified such devices as
“machinegun[s]” since 1982. See Record 1077. In 2003, the Fifth
Circuit held that such a contraption qualified as a “machinegun”
under the statute. See United States v. Camp , 343 F.3d 743 , 745. An owner of a semiautomatic rifle had placed
a fishing reel inside the weapon’s trigger guard. Id ., at
744. When he pulled a switch behind the original trigger, the
switch supplied power to a motor connected to the fishing reel. Ibid. The motor caused the reel to rotate, and that rotation
manipulated the curved lever, causing it to fire in rapid
succession. Ibid. ATF in 2017 also classified as a
“machinegun” a wearable glove that a shooter could activate to
initiate a mechanized piston moving back and forth, repeatedly
pulling and releasing a semiautomatic rifle’s curved lever. See
Record 1074–1076.[ 7 ]

															The majority tosses aside the presumption
against ineffectiveness, claiming that its interpretation only
“draws a line more narrowly than one of [Congress’s] conceivable
statutory purposes might suggest” because the statute still
regulates “all traditional machineguns” like M16s. Ante, at
18. Congress’s ban on M16s, however, is far less effective if a
shooter can instead purchase a bump stock or construct a device
that enables his AR–15 to fire at the same rate. Even bump-stock
manufacturers recognize that they are exploiting a loophole, with
one bragging on its website “Bumpfire Stocks are the closest you
can get to full auto and still be legal.” Midsouth Shooters,
BUMPFIRE SYSTEMS,
https://www.midsouthshooterssupply.com/b/bumpfire- systems. The
majority creates a definition of the statute that bans only
“traditional” machineguns, even though its definition renders
Congress’s clear intent readily evadable.

															Every Member of the majority has previously
emphasized that the best way to respect congressional intent is to
adhere to the ordinary understanding of the terms Congress uses.
See, e . g ., Jam v. International Finance
Corp. , 586 U.S. 199, 209 (2019) (Roberts, C. J., for the
Court) (“ ‘[T]he legislative purpose is expressed by the
ordinary meaning of the words used’ ”); Gross v. FBL
Financial Services, Inc. , 557 U.S.
167 , 175 (2009) (Thomas, J., for the Court) (“ ‘Statutory
construction must begin with the language employed by Congress and
the assumption that the ordinary meaning of that language
accurately expresses the legislative purpose’ ”); Wall v. Kholi , 562 U.S.
545 , 551 (2011) (Alito, J., for the Court) (“ ‘We give the
words of a statute their ordinary, contemporary, common meaning,
absent an indication Congress intended them to bear some different
import’ ”); BP p.l.c. v. Mayor and City Council of
Baltimore , 593 U.S. 230, 237 (2021) (Gorsuch, J., for the
Court) (“When called on to interpret a statute, this Court
generally seeks to discern and apply the ordinary meaning of its
terms at the time of their adoption”); Sackett v. EPA , 598 U.S. 651, 723, 727 (2023) (Kavanaugh, J.,
concurring in judgment) (reasoning that departing from “all
indications of ordinary meaning” will “create regulatory
uncertainty for the Federal Government . . . and
regulated parties”); Bartenwerfer v. Buckley , 598
U.S. 69, 77, 83 (2023) (Barrett, J., for the Court) (declining to
“artificially narrow ordinary meaning” to “second-guess
[Congress’s] judgment”). Today, the majority forgets that principle
and substitutes its own view of what constitutes a “machinegun” for
Congress’s.

															*  *  *

															Congress’s definition of “machinegun”
encompasses bump stocks just as naturally as M16s. Just like a
person can shoot “automatically more than one shot” with an M16
through a “single function of the trigger” if he maintains
continuous backward pressure on the trigger, he can do the same
with a bump-stock-equipped semiautomatic rifle if he maintains
forward pressure on the gun. §5845(b). Today’s decision to reject
that ordinary understanding will have deadly consequences. The
majority’s artificially narrow definition hamstrings the
Government’s efforts to keep machineguns from gunmen like the Las
Vegas shooter. I respectfully dissent. Notes 1 Congress has twice
strengthened the regulation of machineguns over the years without
substantially updating the definition. See Gun Control Act of 1968,
82Stat. 1213 (expanding registration requirements and strengthening
criminal penalties); Firearms Owners’ Protection Act, 100Stat.
452–453 (making it a federal crime “ ‘to transfer or possess a
machinegun’ ”). 2 Of course, “authoritative
legislative history can be useful, even when the meaning can be
discerned from the statute’s language, to reinforce or to confirm a
court’s sense of the text.” R. Katzmann, Judging Statutes 35
(2014). 3 The majority thinks that
this logic should apply just as well to manual bump firing. Ante, at 14. As described supra , at 5, and infra , at 13, however, bump firing requires much more from
the shooter than the simple forward pressure required to fire a
bump-stock-equipped semiautomatic rifle. 4 The majority claims that
these arguments explain only “why, even assuming a semiautomatic
rifle equipped with a bump stock could fire more than one shot by a
single function of the trigger, it could not do so
‘automatically.’ ” Ante, at 13, n. 6. That is
correct, as far as the majority’s reasoning goes. The majority
defines “ ‘single function of the trigger’ ” as a reset
of a rifle’s internal trigger mechanism. Ante, at 11. A more
accurate definition is the human action required to initiate the
firing sequence. Supra , at 7–10. The majority’s argument for
why “something more than a ‘single function of the trigger’ is
required to fire multiple shots,” ante, at 15, is therefore
relevant to both its discussion of “automatically” and my
discussion of “single function of the trigger.” 5 The majority attempts to
analogize a bump stock to the Model 37 shotgun, which allows the
user to “fire multiple shots by holding down the trigger while
operating the shotgun’s pump action.” Ante, at 16. The Model
37 automates the second process ( i . e ., pulling the
trigger for each shot), as long as the shooter maintains pressure
on the trigger. Unlike a semiautomatic rifle, however, the Model 37
does not automate the first, as the shooter “must manually operate
the pump action with his nontrigger hand” to “ejec[t ] the
spent cartridge and loa[d ] a new one into the chamber.” Ibid. 6 The majority emphasizes
that ATF previously took the position that certain bump-stock
devices were not “machinegun[s]” under the statute. See ante, at 3, 19. ATF, however, has repeatedly classified
other devices that modify semiautomatic rifles by allowing a single
activation of the shooter to automate repeat fire as machineguns.
See, e . g ., 83 Fed. Reg. 66518, n. 4 (referencing
ATF classifications of trigger reset devices); Akins v. United States , 312 F. Appx. 197, 200–201 (CA11 2009)
( per curiam ) (upholding classification of Akins
Accelerator, a spring-operated bump stock); United States v. Camp , 343 F.3d 743 , 745 (CA5 2003) (upholding classification of
fishing reel attached to a rifle trigger that, upon activation,
repeatedly operated the curved lever of the rifle). 7 Respondent does not today
challenge ATF’s classification of these devices as “machinegun[s].”
His lawyer noted at oral argument, however, that “forced reset
triggers” would be part of a category of “harder cases” where
“there may be a question as to what exactly the trigger is and then
how does that trigger function.” Tr. of Oral Arg. 82. That
ambiguity stems from the majority’s loophole for weapons that
require multiple mechanical actions to fire continuously, even when
a shooter initiates that fire with a single human
action.

Summary: The Supreme Court held that a bump stock, an accessory that increases the rate of fire for a semiautomatic rifle, does not convert the rifle into a machine gun as defined by the National Firearms Act of 1934 and affirmed the lower court's decision. The Court's decision centered on the interpretation of the phrase "single function of the trigger," with the majority defining it as the internal trigger mechanism's mechanical process, and the minority arguing it should be defined as the human action required to initiate firing. This decision has implications for the regulation of bump stocks and similar devices, with potential loopholes for weapons that require multiple mechanical actions to fire continuously.