(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. CARGILL

CERTIORARI 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 “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.” 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. Using 

a technique called bump firing, shooters can fire semiautomatic firearms at rates approaching those of some machineguns. A shooter who 

bump 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 bump 

firing, 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 are 

machineguns. 83 Fed. Reg. 13442. ATF’s Rule ordered owners of 

bump stocks either to destroy or surrender them to ATF to avoid criminal prosecution.

 Michael Cargill surrendered two bump stocks to ATF under protest, 
2 GARLAND v. CARGILL 

 

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 a 

bump stock fits the statutory definition of a machinegun and resolved 

that 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, it 

would 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 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.” 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. 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. 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 bump 

the trigger against his stationary finger. Moreover, ATF’s position is 

logically inconsistent because its reasoning would also mean that a 

semiautomatic rifle without a bump stock is capable of firing more 

than 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 
Cite as: 602 U. S. ____ (2024) 3 

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” “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. By contrast, pushing forward on the front grip of 

a 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 a 

shooter is less physically involved with operating a bump-stock 

equipped rifle than operating the Model 37. It explains that once a 

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. 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). 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] 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. 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 
4 GARLAND v. CARGILL

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 ineffectiveness 

cannot do the work that ATF asks of it. Interpreting §5845(b) to exclude semiautomatic rifles equipped with bump stocks comes nowhere 

close 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.
Cite as: 602 U. S. ____ (2024) 1

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 of 

Decisions, 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 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 
2 GARLAND v. CARGILL

Opinion of the Court

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 
Cite as: 602 U. S. ____ (2024) 3

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 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 

——————

1Some 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.
4 GARLAND v. CARGILL

Opinion of the Court

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 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, 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:
Cite as: 602 U. S. ____ (2024) 5

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 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, 
6 GARLAND v. CARGILL

Opinion of the Court

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.

——————

2See, 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).
Cite as: 602 U. S. ____ (2024) 7

Opinion of the Court

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 trig-
8 GARLAND v. CARGILL

Opinion of the Court

ger 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 

——————

3These illustrations are found in the Brief for FPC Action Foundation 

as Amicus Curiae 14–15.
Cite as: 602 U. S. ____ (2024) 9

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 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.
10 GARLAND v. CARGILL

Opinion of the Court

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 
Cite as: 602 U. S. ____ (2024) 11

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 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 

——————

4Machinegun 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.

5An animated graphic that displays the relevant movements is available at https://www.supremecourt.gov/media/images/AR-15.gif.
12 GARLAND v. CARGILL

Opinion of the Court

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 
Cite as: 602 U. S. ____ (2024) 13

Opinion of the Court

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 

——————

6The 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.
14 GARLAND v. CARGILL

Opinion of the Court

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” 
Cite as: 602 U. S. ____ (2024) 15

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, 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 

——————

7The 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”).
16 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 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 
Cite as: 602 U. S. ____ (2024) 17

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 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 

——————

8The 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.
18 GARLAND v. CARGILL

Opinion of the Court

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.
Cite as: 602 U. S. ____ (2024) 19

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 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.

——————

9The 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).
Cite as: 602 U. S. ____ (2024) 1 

ALITO, J., concurring

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.
Cite as: 602 U. S. ____ (2024) 1 

SOTOMAYOR, J., dissenting

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 
2 GARLAND v. CARGILL

SOTOMAYOR, J., dissenting

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, 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., 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 
Cite as: 602 U. S. ____ (2024) 3 

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 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 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 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, 48 Stat. 1236. That 

essential definition still governs today. See 26 U. S. C. 

§5845(b).1

—————— 1Congress 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 and 

strengthening criminal penalties); Firearms Owners’ Protection Act, 100 
4 GARLAND v. CARGILL

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 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. 

—————— 

Stat. 452–453 (making it a federal crime “‘to transfer or possess a machinegun’”).
Cite as: 602 U. S. ____ (2024) 5 

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 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 
6 GARLAND v. CARGILL

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 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, 
Cite as: 602 U. S. ____ (2024) 7 

SOTOMAYOR, J., dissenting

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 bumpstock-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. 
8 GARLAND v. CARGILL

SOTOMAYOR, J., dissenting

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 
Cite as: 602 U. S. ____ (2024) 9 

SOTOMAYOR, J., dissenting

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 

—————— 2Of 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).
10 GARLAND v. CARGILL

SOTOMAYOR, J., dissenting

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 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 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 

—————— 3The 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. 4The majority claims that these arguments explain only “why, even 

assuming a semiautomatic rifle equipped with a bump stock could fire 
Cite as: 602 U. S. ____ (2024) 11

SOTOMAYOR, J., dissenting

fire an M16 from that required to fire a bump-stockequipped 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-stockequipped 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 

—————— 

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.”
12 GARLAND v. CARGILL

SOTOMAYOR, J., dissenting

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 

—————— 5The 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 
Cite as: 602 U. S. ____ (2024) 13

SOTOMAYOR, J., dissenting

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-stockequipped 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” 

—————— 

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.
14 GARLAND v. CARGILL

SOTOMAYOR, J., dissenting

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 bumpstock 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 
Cite as: 602 U. S. ____ (2024) 15

SOTOMAYOR, J., dissenting

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 

—————— 6The 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).
16 GARLAND v. CARGILL

SOTOMAYOR, J., dissenting

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- 

—————— 7Respondent 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.
Cite as: 602 U. S. ____ (2024) 17

SOTOMAYOR, J., dissenting

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 
18 GARLAND v. CARGILL

SOTOMAYOR, J., dissenting

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.