GARLAND v. CARGILL

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

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

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

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

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

I

A

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

 Congress responded in 1934 by sharply restricting civilian ownership of machineguns. See National Firearms Act of 1934, §§3–6, 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  variety of ways. Some would fire continuously with a single pull of the trigger or push of a button. See Charles Brief 7, and n. 12 (noting that a Browning M1918 rifle fired eight rounds “ ‘in a second with one pull of the trigger’ ”); see also Brief for Petitioners 22 (noting that a Browning M2 fired with a push of the thumb). Others, such as the famous Thompson Submachine Gun Caliber .45, or “Tommy Gun,” would fire continuously only so long as the shooter maintained backward pressure on the trigger; a shooter could still fire single shots by pulling and releasing the trigger each time. See Test of Thompson Submachine Gun, 69 Army and Navy Register 355 (Apr. 9, 1921) (noting that the shooter of a Tommy Gun “can fire the contents of the magazine with a single prolonged pull or fire a single shot by merely releasing the trigger”). The internal mechanisms of automatic-fire weapons also varied enormously, with many (such as the Tommy Gun) relying principally on the recoil energy produced by each bullet’s discharge to effectuate automatic fire. See, e.g., War Dept., Basic Field Manual: Thompson Submachine Gun, Caliber .45, M1928A1, p. 1 (1941) (“The Thompson submachine gun . . . is an air-cooled, recoil-operated, magazine-fed weapon”); W. Smith, Small Arms of the World: The Basic Manual of Military Small Arms 165 (1955) (describing Tommy guns as “recoil operated weapons on the elementary blowback principle”).

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

 B

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

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

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

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

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

II

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

 This is not a hard case. All of the textual evidence points to the same interpretation. A bump-stock-equipped semiautomatic rifle is a machinegun because (1) with a single pull of the trigger, a shooter can (2) fire continuous shots without any human input beyond maintaining forward pressure. The majority looks to the internal mechanism that initiates fire, rather than the human act of the shooter’s initial pull, to hold that a “single function of the trigger” means a reset of the trigger mechanism. Its interpretation requires six diagrams and an animation to decipher the meaning of the statutory text. See ante, at 8–11,  and n. 5. Then, shifting focus from the internal mechanism of the gun to the perspective of the shooter, the majority holds that continuous forward pressure is too much human input for bump-stock-enabled continuous fire to be “automatic.” See ante, at 14–17.

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

A

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

 Consider the relevant dictionary definitions. In 1934, when Congress passed the National Firearms Act, “function” meant “the mode of action by which [something] fulfils its purpose.” 4 Oxford English Dictionary 602 (1933). A “trigger” meant the “movable catch or lever” that “sets some force or mechanism in action.” 11 id., at 357. The majority agrees with those definitions. Ante, at 7. It errs, however, by maintaining a myopic focus on a trigger’s mechanics rather than on how a shooter uses a trigger to initiate fire. Ibid.

 Nothing about those definitions suggests that “function of the trigger” means the mechanism by which the trigger resets mechanically to fire a second shot. See ante, at 8–11 (explaining the interior mechanics of an AR–15 trigger mechanism), as opposed to the process that a pull of the trigger on a bump-stock-equipped semiautomatic rifle sets in motion. The most important “function” of a “trigger” is what it enables a shooter to do; what “force or mechanism” it sets “in action.” 11 Oxford English Dictionary, at 357. A “single function of the trigger” more naturally means a single initiation of the firing sequence. Regardless of what is happening in the internal mechanics of a firearm, if a shooter must activate the trigger only a single time to initiate a firing sequence that will shoot “automatically more than one shot,” that firearm is a “machinegun.” §5845(b).

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

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

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

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

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

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

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

B

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

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

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

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

C

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

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

 Moreover, bump stocks are not the only devices that transform semiautomatic rifles into weapons capable of rapid fire with a single function of the trigger. Recognizing the creativity of gun owners and manufacturers, Congress wrote a statute “loaded with anticircumvention devices.” Tr. of Oral Arg. 68. The definition of “machinegun” captures “any weapon which shoots, is designed to shoot, or can be readily restored to shoot, automatically more than one shot, without manual reloading, by a single function of the trigger.” §5845(b). Not “more than four, five, or six shots,” not “single pull” or “single push” of the trigger.” Following that definition, the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) has reasonably classified many transformative devices other than bump stocks as “machinegun[s].”⁶ For instance, ATF has long classified “forced reset triggers” as machineguns. See Brief for Petitioners 28. A forced reset trigger includes a device that forces the trigger back downward after the shooter’s initial pull, repeatedly pushing the curved lever against the shooter’s stationary trigger finger. See ibid. To a shooter, a semiautomatic rifle equipped with a forced reset trigger feels much like an M16. He must pull the trigger only once and then maintain pressure to achieve continuous fire. See ibid.

 Gun owners themselves also have built motorized devices that will repeatedly pull a semiautomatic firearm’s curved  lever to enable continuous fire. ATF has classified such devices as “machinegun[s]” since 1982. See Record 1077. In 2003, the Fifth Circuit held that such a contraption qualified as a “machinegun” under the statute. See United States v. Camp, 343 F. 3d 743, 745. An owner of a semiautomatic rifle had placed a fishing reel inside the weapon’s trigger guard. Id., at 744. When he pulled a switch behind the original trigger, the switch supplied power to a motor connected to the fishing reel. Ibid. The motor caused the reel to rotate, and that rotation manipulated the curved lever, causing it to fire in rapid succession. Ibid. ATF in 2017 also classified as a “machinegun” a wearable glove that a shooter could activate to initiate a mechanized piston moving back and forth, repeatedly pulling and releasing a semiautomatic rifle’s curved lever. See Record 1074–1076.⁷

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

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

*  *  *

 Congress’s definition of “machinegun” encompasses bump stocks just as naturally as M16s. Just like a person  can shoot “automatically more than one shot” with an M16 through a “single function of the trigger” if he maintains continuous backward pressure on the trigger, he can do the same with a bump-stock-equipped semiautomatic rifle if he maintains forward pressure on the gun. §5845(b). Today’s decision to reject that ordinary understanding will have deadly consequences. The majority’s artificially narrow definition hamstrings the Government’s efforts to keep machineguns from gunmen like the Las Vegas shooter. I respectfully dissent.