(Slip Opinion)

OCTOBER TERM, 2023

1

Syllabus
NOTE: Where it is feasible, a syllabus (headnote) will be released, as is
being done in connection with this case, at the time the opinion is issued.
The syllabus constitutes no part of the opinion of the Court but has been
prepared by the Reporter of Decisions for the convenience of the reader.
See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337.

SUPREME COURT OF THE UNITED STATES
Syllabus

GARLAND, ATTORNEY GENERAL, ET AL. v. CARGILLCERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR
THE FIFTH CIRCUIT
No. 22–976.

Argued February 28, 2024—Decided June 14, 2024

The National Firearms Act of 1934 defines a “machinegun” as “anyweapon 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.” 26 U. S. C. §5845(b). 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. Usinga technique called bump firing, shooters can fire semiautomatic firearms at rates approaching those of some machineguns. A shooter whobump fires a rifle uses the firearm’s recoil to help rapidly manipulate
the trigger. Although bump firing does not require any additional
equipment, a “bump stock” is an accessory designed to make the technique easier. A bump stock does not alter the basic mechanics of bumpfiring, and the trigger still must be released and reengaged to fire each
additional shot.
For many years, the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) consistently took the position that semiautomatic rifles
equipped with bump stocks were not machineguns under §5845(b).
ATF abruptly changed course when a gunman using semiautomatic
rifles equipped with bump stocks fired hundreds of rounds into a crowd
in Las Vegas, Nevada, killing 58 people and wounding over 500 more.
ATF subsequently proposed a rule that would repudiate its previous
guidance and amend its regulations to “clarify” that bump stocks aremachineguns. 83 Fed. Reg. 13442. ATF’s Rule ordered owners ofbump stocks either to destroy or surrender them to ATF to avoid criminal prosecution.
Michael Cargill surrendered two bump stocks to ATF under protest,

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Syllabus
then filed suit to challenge the Rule under the Administrative Procedure Act. As relevant, Cargill alleged that ATF lacked statutory authority to promulgate the 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 Fifth Circuit initially affirmed,
but reversed after rehearing en banc. A majority agreed that §5845(b)is ambiguous as to whether a semiautomatic rifle equipped with abump stock fits the statutory definition of a machinegun and resolvedthat ambiguity in Cargill’s favor.
Held: ATF exceeded its statutory authority by issuing a Rule that classifies a bump stock as a “machinegun” under §5845(b). Pp. 6–19.
(a) A semiautomatic rifle equipped with a bump stock is not a “machinegun” as defined by §5845(b) because: (1) it cannot fire more than
one shot “by a single function of the trigger” and (2) even if it could, itwould not do so “automatically.” ATF therefore exceeded its statutory
authority by issuing a Rule that classifies bump stocks as machineguns. P. 6.
(b) A semiautomatic rifle equipped with a bump stock does not fire
more than one shot “by a single function of the trigger.” The phrase“function of the trigger” refers to the mode of action by which the trigger activates the firing mechanism. No one disputes that a semiautomatic rifle without a bump stock is not a machinegun because ashooter must release and reset the trigger between every shot. And,any subsequent shot fired after the trigger has been released and resetis the result of a separate and distinct “function of the trigger.” Nothing changes when a semiautomatic rifle is equipped with a bump stock.
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.
ATF argues that a shooter using a bump stock must pull the trigger
only one time to initiate a bump-firing sequence of multiple shots. Thisinitial 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. This argument rests on the
mistaken premise that there is a difference between the shooter flexing
his finger to pull the trigger and pushing the firearm forward to bumpthe trigger against his stationary trigger. Moreover, ATF’s position is
logically inconsistent because its reasoning would also mean that asemiautomatic rifle without a bump stock is capable of firing morethan one shot by a “single function of the trigger.” Yet, ATF agrees
that is not the case. ATF’s argument is thus at odds with itself. Pp.
7–14.
(c) Even if a semiautomatic rifle with a bump stock could fire more

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Syllabus
than one shot “by a single function of the trigger,” it would not do so“automatically.” Section 5845(b) 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. Firing multiple shots using a semiautomatic rifle with a bump stock requires more than a single function of
the trigger. A shooter must maintain forward pressure on the rifle’s
front grip with his nontrigger hand. Without this ongoing manual input, a semiautomatic rifle with a bump stock will not fire multiple
shots.
ATF counters that machineguns also require continuous manual input from a shooter: The shooter must both engage the trigger and keep
it pressed down to continue shooting. ATF argues 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” “bya single function of the trigger.” Simply pressing and holding the trigger down on a fully automatic rifle is not manual input in addition toa trigger’s function. By contrast, pushing forward on the front grip ofa semiautomatic rifle equipped with a bump stock is not part of functioning the trigger.
Moreover, a semiautomatic rifle with a bump stock is indistinguishable from the Ithaca Model 37 shotgun, a weapon the ATF concedes
cannot fire multiple shots “automatically.” ATF responds that ashooter is less physically involved with operating a bump-stock
equipped rifle than operating the Model 37. It explains that once ashooter pulls the rifle’s trigger a single time, the bump stock harnesses
the firearm’s recoil energy in a continuous back-and-forth cycle thatallows the shooter to attain continuous firing. But, even if one aspectof a weapon’s operation could be seen as “automatic,” that would notmean the weapon “shoots . . . automatically more than one shot . . . bya single function of the trigger.” §5845(b) (emphasis added). Pp. 14–17.
(d) Abandoning the text, ATF attempts to shore up its position by
relying on the presumption against ineffectiveness. That presumption
weighs against interpretations of a statute that would “rende[r] thelaw in a great measure nugatory, and enable offenders to elude its provisions in the most easy manner.” The Emily, 9 Wheat. 381, 389. In
ATF’s view, Congress “restricted machineguns because they eliminate
the manual movements that a shooter would otherwise need to makein 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

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Syllabus
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. The presumption against ineffectivenesscannot do the work that ATF asks of it. Interpreting §5845(b) to exclude semiautomatic rifles equipped with bump stocks comes nowhereclose to making the statute useless. Pp. 17–19.

57 F. 4th 447, affirmed.
THOMAS, J. delivered the opinion of the Court, in which ROBERTS, C. J.,
and ALITO, GORSUCH, KAVANAUGH, and BARRETT, JJ., joined. ALITO, J.,
filed a concurring opinion. SOTOMAYOR, J., filed a dissenting opinion, in
which KAGAN and JACKSON, JJ., joined.

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Opinion of the Court
NOTICE: This opinion is subject to formal revision before publication in the
United States Reports. Readers are requested to notify the Reporter ofDecisions, Supreme Court of the United States, Washington, D. C. 20543,
pio@supremecourt gov, of any typographical or other formal errors.

SUPREME COURT OF THE UNITED STATES_________________

No. 22–976_________________MERRICK B. GARLAND, ATTORNEY GENERAL, ET AL.,PETITIONERS v. MICHAEL CARGILLON 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 thetrigger.” 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. Thiscase 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 notand therefore affirm.
I
A
Under the National Firearms Act of 1934, a “machinegun” is “any weapon which shoots, is designed toshoot, or can be readily restored to shoot, automaticallymore 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

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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 andreengage the trigger to fire another shot. Machineguns canordinarily achieve higher rates of fire than semiautomatic
firearms because the shooter does not need to release andreengage 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 therifle 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 handto 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 bumpthe trigger with sufficient force to engage it. But, if theshooter applies too much forward pressure, the rifle will notslide back far enough to allow the trigger to reset. The rightbalance produces a reciprocating motion that permits theshooter to repeatedly engage and release the trigger in
rapid succession.
Although bump firing does not require any additional

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Opinion of the Court

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 backand forth. This casing helps manage the back-and-forthmotion required for bump firing. A bump stock also has aledge 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 stillmust 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 definedby §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 notmachineguns 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 bumpstock 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, eachsucceeding 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——————
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.

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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 tooutlaw bump stocks nationwide. Within days, Members ofCongress 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); seealso H. R. 3947, 115th Cong., 1st Sess. (2017); H. R. 3999,
115th Cong., 1st Sess. (2017). None of these bills becamelaw. 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 thatwould amend its regulations to “clarify” that bump stocks
are machineguns. 83 Fed. Reg. 13442 (2018). ATF’s aboutface 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, explainingthat 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 bumpstocks.’ ” Ibid.
ATF issued its final Rule in 2018. 83 Fed. Reg. 66514.
The agency’s earlier regulations simply restated §5845(b)’sstatutory definition. Ibid. The final Rule amended thoseregulations by adding the following language:

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Opinion of the Court“[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 selfregulating 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 thetrigger 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 therecoil energy of the semi-automatic firearm to which it
is affixed so that the trigger resets and continues firingwithout 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 ofbump 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 abench 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,

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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 therule of lenity required resolving that ambiguity in Cargill’sfavor. 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 . . . bya 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 asplit among the Courts of Appeals regarding whether bumpstocks 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 . . . bya 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 asingle 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 bumpstocks as machineguns.

——————
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).

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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 thetrigger.” All that a bump stock does is accelerate the rateof 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 catchor 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 torelease 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 metallever. 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 abump stock is not a machinegun because it fires only one
shot per “function of the trigger.” That is, engaging the trig-

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ger a single time will cause the firing mechanism to discharge only one shot. To understand why, it is helpful toconsider 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., thebarrel) 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 intoa 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 thefiring pin, causing a shot to fire. Ibid. The disconnector isthe component responsible for resetting the hammer to its——————
3 These illustrations are found in the Brief for FPC Action Foundationas Amicus Curiae 14–15.

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Opinion of the Court

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 thetrigger pivots downward and out of the notch securing thehammer. 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.

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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 thesame 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 thechamber. Ibid. The disconnector will hold the hammer inCite as: 602 U. S. ____ (2024)

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Opinion of the Court

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 andallows it to move forward (as indicated by the arrow), thehammer slips off the disconnector just as the square pointof the trigger rises into the notch on the hammer (circled
above). Ibid. The trigger mechanism is thereby reset to theoriginal 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——————
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 isloaded 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 tofire 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 .

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by engaging the trigger a second time and thereby initiatinga 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 aseparate and distinct “function of the trigger.”
Nothing changes when a semiautomatic rifle is equippedwith a bump stock. The firing cycle remains the same. Between every shot, the shooter must release pressure fromthe trigger and allow it to reset before reengaging the trigger for another shot. A bump stock merely reduces theamount of time that elapses between separate “functions”
of the trigger. The bump stock makes it easier for theshooter to move the firearm back toward his shoulder andthereby 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 bumpstock, 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 functionof 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 tocontinue firing “without additional physical manipulationof 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

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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 tobump the trigger against his stationary finger. ATF andthe 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 thetrigger—whether it be a pull, bump, or something else. Nordoes 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 theshooter engages the trigger. And, as we have explained, asemiautomatic rifle will fire only one shot each time theshooter engages the trigger—with or without a bumpstock.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” toinclude not only “a single pull of the trigger” but also any“analogous motions.” 83 Fed. Reg. 66553. ATF concedesthat one such analogous motion that qualifies as a single
function of the trigger is “sliding the rifle forward” to bumpthe trigger. Brief for Petitioners 22. But, if that is true,
then every bump is a separate “function of the trigger,” andsemiautomatic rifles equipped with bump stocks are therefore not machineguns. ATF resists the natural implication——————
6 The dissent says that we “resis[t]” the “ordinary understanding of theterm ‘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 bya single function of the trigger, it could not do so “automatically.” Seeinfra, at 14–17. Those arguments have nothing to do with our explanation of what a “single function of the trigger” means. Ibid.

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Opinion of the Courtof its reasoning, insisting that the bumping motion is a“function of the trigger” only when it initiates, but not whenit continues, a firing sequence. But, Congress did not writea 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 islogically inconsistent. They reason that a semiautomatic
rifle equipped with a bump stock fires more than one shotby a single function of the trigger because a shooter “needonly 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 shouldbe true for a semiautomatic rifle without a bump stock. After all, as the dissent and ATF themselves acknowledge, ashooter manually bump firing a semiautomatic rifle canachieve 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 atodds with itself.
We conclude that semiautomatic rifle equipped with abump 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,” itwould 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”

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Opinion of the Court

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, theweapon 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 abump stock requires more than a single function of the trigger. A shooter must also actively maintain just the rightamount 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 notbump 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 thetrigger one time—and then some.7
ATF and the dissent counter that machineguns also require continuous manual input from a shooter: He must——————
7 The dissent seemingly concedes this point, repeatedly recognizingthat 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 isa 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 thetrigger, if he maintains continuous forward pressure on the gun, thebump stock harnesses the recoil to move the curved lever back and forth
against his finger”).

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GARLAND v. CARGILL
Opinion of the Court

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 functionin 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 thefront grip will not cause the weapon to fire unless theshooter 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 thesame result only by a single function of the trigger and thensome.
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 thespent 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 theshooter 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 amountof forward pressure on the front grip of a bump-stock
equipped rifle is no less additional input than is operating

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Opinion of the Court

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 thefirearm’s recoil energy in a continuous back-and-forth cyclethat allows the shooter to attain continuous firing.” Id., at66519. 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). Afterall, many weapons have some “automatic” features. For example, semiautomatic rifles eject the spent cartridge fromthe 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 sensethat 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 asingle function of the trigger” because the shooter must do
more than simply engage the trigger one time. The same istrue 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 doso “automatically.”C
Abandoning the text, ATF and the dissent attempt toshore up their position by relying on the presumption——————
8 The dissent attempts to undermine this analogy by pointing out thata Model 37 requires manual reloading and therefore cannot qualify as amachinegun under §5845(b). Post, at 12–13, n. 5. But, that is beside thepoint. 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.

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GARLAND v. CARGILL
Opinion of the Court

against ineffectiveness. That presumption weighs againstinterpretations of a statute that would “rende[r] the law ina 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 notenact 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 arelawful “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 thework that ATF and the dissent ask of it. A law is not uselessmerely because it draws a line more narrowly than one ofits conceivable statutory purposes might suggest. Interpreting §5845(b) to exclude semiautomatic rifles equippedwith 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 thelaw 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. Seepost, at 14–17, and n. 6.

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Opinion of the Court

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 bumpstock-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 anunmodified semiautomatic rifle using the manual bump-firing technique. See post, at 5. The dissent thus fails to provethat our reading makes §5845(b) “far less effective,” muchless 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 thebanner of speculation about what Congress might havedone.” Henson v. Santander Consumer USA Inc., 582 U. S.
79, 89 (2017).9III
For the foregoing reasons, we affirm the judgment of the
Court of Appeals.
It is so ordered.
——————
9 The dissent concludes by claiming that our interpretation of §5845(b)“renders Congress’s clear intent readily evadable.” Post, at 17. And, ithighlights that “[e]very Member of the majority has previously emphasized that the best way to respect congressional intent is to adhere to theordinary 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 fromthe 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).

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1

ALITO, J., concurring

SUPREME COURT OF THE UNITED STATES_________________

No. 22–976_________________MERRICK B. GARLAND, ATTORNEY GENERAL, ET AL.,PETITIONERS v. MICHAEL CARGILLON 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 noother 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 equippedwith a bump stock. But the statutory text is clear, and wemust follow it.
The horrible shooting spree in Las Vegas in 2017 did notchange 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 ofbump stocks and machineguns. Congress can amend thelaw—and perhaps would have done so already if ATF had
stuck with its earlier interpretation. Now that the situation
is clear, Congress can act.

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1

SOTOMAYOR, J., dissenting

SUPREME COURT OF THE UNITED STATES_________________

No. 22–976_________________MERRICK B. GARLAND, ATTORNEY GENERAL, ET AL.,PETITIONERS v. MICHAEL CARGILLON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF
APPEALS FOR THE FIFTH CIRCUIT[June 14, 2024]

JUSTICE SOTOMAYOR, with whom JUSTICE KAGAN andJUSTICE 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 andwounded over 500. He did so by affixing bump stocks tocommonly available, semiautomatic rifles. These simple
devices harness a rifle’s recoil energy to slide the rifle backand 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 bumpstock 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 thetrigger.” 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

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GARLAND v. CARGILL
SOTOMAYOR, J., dissenting

ordinary meaning of the statutory text and unsupported bycontext or purpose. When I see a bird that walks like a
duck, swims like a duck, and quacks like a duck, I call thatbird 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 originallymarketed 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, 48 Stat. 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., 2dSess., 1–2. “[W]hile there is justification for permitting thecitizen 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

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SOTOMAYOR, J., dissenting

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 eightrounds “ ‘in a second with one pull of the trigger’ ”); see also
Brief for Petitioners 22 (noting that a Browning M2 firedwith 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 theshooter 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 ofautomatic-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 aircooled, 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 whichshoots, or is designed to shoot, automatically . . . more than
one shot, without manual reloading, by a single function of
the trigger.” National Firearms Act, 48 Stat. 1236. Thatessential definition still governs today. See 26 U. S. C.
§5845(b). 1——————
1 Congress has twice strengthened the regulation of machineguns over
the years without substantially updating the definition. See Gun Control Act of 1968, 82 Stat. 1213 (expanding registration requirements andstrengthening criminal penalties); Firearms Owners’ Protection Act, 100

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SOTOMAYOR, J., dissenting

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 afire 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 mechanismof 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 shoteach 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 thesights 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 regularperson with an AR–15 can achieve a fire rate of around 60
rounds per minute, with one pull of the trigger per second.
——————
Stat. 452–453 (making it a federal crime “ ‘to transfer or possess a machinegun’ ”).

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SOTOMAYOR, J., dissenting

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 fromthe first shot to fire the rifle continuously. See 83 Fed. Reg.
66532–66533 (2018). To use a belt loop, he must hold therifle low against his hip, put his finger in the trigger guard,
and then loop his finger through a belt loop on his pants tolock 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 canalso use a rubber band or zip tie to tie a finger close to thetrigger. See id., at 66532. If the shooter is strong andskilled 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 thepart held against the shoulder. See id., at 66516. A bumpstock, 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 canplace his finger while shooting, and a “receiver module” thatguides and regulates the weapon’s recoil. Ibid. To fire asemiautomatic rifle equipped with a bump stock, theshooter either pulls the trigger, see ibid., or slides the gun

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SOTOMAYOR, J., dissenting

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 bumpstocks, which “conver[t]” semiautomatic rifles so that a single pull of the trigger provides continuous fire as long as theshooter 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 mechanismthat initiates fire, rather than the human act of theshooter’s initial pull, to hold that a “single function of thetrigger” 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,

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SOTOMAYOR, J., dissenting

and n. 5. Then, shifting focus from the internal mechanismof 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 thisCourt’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 bumpstock-equipped semiautomatic rifle, the trigger’s internalmechanism 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 thehuman 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 someforce 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.

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GARLAND v. CARGILL
SOTOMAYOR, J., dissenting

Ibid.
Nothing about those definitions suggests that “functionof 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 thetrigger on a bump-stock-equipped semiautomatic rifle sets
in motion. The most important “function” of a “trigger” iswhat 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 ishappening in the internal mechanics of a firearm, if ashooter must activate the trigger only a single time to initiate a firing sequence that will shoot “automatically morethan 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 onWays and Means, 73d Cong., 2d Sess., 38–40 (1934). He
understood the “distinguishing feature of a machine gun [tobe] that by a single pull of the trigger the gun continues tofire.” Id., at 40. He emphasized that a firearm “which iscapable of firing more than one shot by a single pull of thetrigger, 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 thesecond shot to be fired.” Id., at 41. He did not say “thehammer slips off the disconnector just as the square pointof 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

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SOTOMAYOR, J., dissenting

the shooter, who must repeatedly activate the trigger foreach 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 thestatute “contains the usual definition of machine gun as aweapon 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 evidenceof contemporaneous understanding. Cf. McDonald v. Chicago, 561 U. S. 742, 828 (2010) (THOMAS, J., concurring inpart and concurring in judgment) (“Statements by legislators can assist . . . to the extent they demonstrate the manner in which the public used or understood a particularword 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’ referredto 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, themajority 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 definitionof “machinegun” in this exact statute to refer to the action——————
2 Of course, “authoritative legislative history can be useful, even whenthe 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).

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GARLAND v. CARGILL
SOTOMAYOR, J., dissentingof 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 (atmost) 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 bumpstock-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 thetrigger and maintain backward pressure (on the trigger), a
shooter of a bump-stock-equipped AR–15 need only pull thetrigger and maintain forward pressure (on the gun). Bothshooters 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 initialaction (that is, one “single function of the trigger”) from theshooter combined with continuous pressure to activate continuous fire. 3
The majority resists this ordinary understanding of theterm “function of the trigger” with two technical arguments. 4 First, it attempts to contrast the action required to——————
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, evenassuming a semiautomatic rifle equipped with a bump stock could fireCite as: 602 U. S. ____ (2024)

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SOTOMAYOR, J., dissenting

fire an M16 from that required to fire a bump-stockequipped AR–15. The majority argues that “holding thetrigger down on a fully automatic rifle is not manual input
in addition to a trigger’s function—it is what causes thetrigger 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, neednot “pull” the trigger to fire. Instead, he need only place afinger 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 thetrigger” to a single mechanism for activating continuous
fire. See ante, at 14–15. A shooter can fire a bump-stockequipped semiautomatic rifle in two ways. First, he canchoose to fire single shots via distinct pulls of the trigger
without exerting any additional pressure. Second, he canfire continuously via maintaining constant forward pressure on the barrel or front grip. The majority holds that theforward pressure cannot constitute a “single function of thetrigger” 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 ofregulated machineguns in 1934 and today. Both weapons
can fire either automatically or semiautomatically. A
shooter using a Tommy Gun in automatic mode could——————
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’ ” asa 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.”

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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 holddown 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 andpushing 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 thegun; and (2) he had to pull the trigger again. A semiautomatic weapon like an AR–15 already automates the firstprocess. The bump stock automates the second. 5 In a fully——————
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 eachshot), as long as the shooter maintains pressure on the trigger. Unlike a

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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 thetrigger, if he maintains continuous forward pressure on thegun, 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 enoughhold 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 anddistance of the recoil, and the finger rest obviates the needto maintain a stationary finger position. All a shooter must
do is rest his finger and press forward on the front grip orbarrel for the rifle to fire continuously.
The majority nevertheless concludes that a bump-stockequipped semiautomatic rifle requires too much human input to fire “automatic[ally]” because it requires the “properamount of forward pressure on the front grip” to maintaincontinuous 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”——————
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 thechamber.” Ibid.

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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).
CThis Court has repeatedly avoided interpretations of astatute that would facilitate its ready “evasion” or “enableoffenders 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 bumpstock users to circumvent Congress’s ban on weapons thatshoot rapidly via a single action of the shooter.
“The presumption against ineffectiveness ensures that atext’s manifest purpose is furthered, not hindered.” Ibid.
Before machineguns, a shooter could fire a gun only as fastas 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

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pull of the trigger.
Moreover, bump stocks are not the only devices thattransform 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 canbe readily restored to shoot, automatically more than one
shot, without manual reloading, by a single function of thetrigger.” §5845(b). Not “more than four, five, or six shots,”
not “single pull” or “single push” of the trigger.” Followingthat 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 thetrigger 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 thenmaintain pressure to achieve continuous fire. See ibid.
Gun owners themselves also have built motorized devices
that will repeatedly pull a semiautomatic firearm’s curved——————
6 The majority emphasizes that ATF previously took the position thatcertain 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 theshooter 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, uponactivation, repeatedly operated the curved lever of the rifle).

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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 UnitedStates 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 behindthe original trigger, the switch supplied power to a motor
connected to the fishing reel. Ibid. The motor caused thereel to rotate, and that rotation manipulated the curved
lever, causing it to fire in rapid succession. Ibid. ATF in2017 also classified as a “machinegun” a wearable glovethat a shooter could activate to initiate a mechanized piston
moving back and forth, repeatedly pulling and releasing asemiautomatic rifle’s curved lever. See Record 1074–1076. 7
The majority tosses aside the presumption against ineffectiveness, claiming that its interpretation only “draws aline more narrowly than one of [Congress’s] conceivablestatutory 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 stillbe legal.” Midsouth Shooters, BUMPFIRE SYSTEMS,
https://www.midsouthshooterssupply.com/b/bumpfire——————
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 thenhow 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 thatfire with a single human action.

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systems. The majority creates a definition of the statutethat bans only “traditional” machineguns, even though its
definition renders Congress’s clear intent readily evadable.
Every Member of the majority has previously emphasizedthat 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]helegislative 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 employedby Congress and the assumption that the ordinary meaningof 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 injudgment) (reasoning that departing from “all indicationsof 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

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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 thesame with a bump-stock-equipped semiautomatic rifle if hemaintains forward pressure on the gun. §5845(b). Today’s
decision to reject that ordinary understanding will havedeadly 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.