The Supreme Court’s 6-3 ruling in Garland v. Cargill was based purely on the statutory text. The National Firearms Act defines “machinegun” as “any weapon which shoots ... automatically more than one shot, without manual reloading, by a single function of the trigger....” A bump stock is a device that allows a semiautomatic rifle to fire more rapidly by pulling the trigger and maintaining forward pressure on the handguard, which harnesses recoil to continue firing.

The opinion by Justice Clarence Thomas includes extensive technical information on how the internal parts of AR-15 rifles function, including diagrams and an animated graphic showing the movement of the parts. Firing a rifle with a bump stock still requires a separate function of the trigger for each shot, and it is not “automatic” because it will not fire without constant manual pressure on the handguard. The Court has never before ventured into such a detailed explanation about how a firearm works.

While the Court’s discussion of how the trigger, sear, disconnector, and bolt interact in the firing sequence is quite technical, the decision embodies broader implications that are significant in other contexts.

First, it is settled once and for all that a semiautomatic is not a machinegun. That should be a no-brainer, but plaintiffs alleged that AR-15s are machineguns in the Las Vegas, Highland Park, and Mexico civil lawsuits. Here’s what the Court said: “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.’”

And dissenting, Justice Sonya Sotomayor agreed: “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.” While the term “assault rifle” is misplaced as applied to a semiautomatic, she correctly referred to “the military’s standard-issue M16 assault rifle” as “the archetypal modern ‘machinegun.’”

Second, Justice Sotomayor referred to AR-15s as “commonly available, semiautomatic rifles.” Recall that the Court in Heller said that firearms “in common use” are protected by the Second Amendment. Some courts that have upheld “assault weapon” bans claiming that AR-15s are not in common use, even though tens of millions of Americans own them.

Third, Cargill was decided solely on the statutory text. No “divine right of deference” was accorded to ATF. Had it claimed deference, it would have raised the issue of which ATF to defer to? The Court notes: “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.’” And any day now we’ll learn if the Chevron deference ship will sink in Loper Bright Enterprises v. Raimondo.

Fourth, the statute being clear, the Court had no need to decide whether the rule of lenity applied, although the majority of judges in the Fifth Circuit decision thought that it did. That avoided the issue in Wooden v. U.S., where Justice Gorsuch supported application of the rule that “penal laws should be construed strictly” if they are “ambiguous,” while Justice Kavanaugh thought the rule should apply only if a law is “grievously ambiguous.”

Fifth, the supposed purposes of a criminal law do not override its explicit text. Cargill states that a semiautomatic with a bump stock is not a machinegun, even though it allows the rifle to “achieve a high rate of fire.” It adds: “A bump stock does not convert a semiautomatic rifle into a machinegun any more than a shooter with a lightning-fast trigger finger does.”

Justice Sotomayor thought the “high rate of fire” to be significant, adding: “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.” Yet nothing in the definition of “machinegun” refers to the rate of fire. If a strange weapon is designed to fire automatically with a single function of the trigger, it would still be a machinegun even if it only fires one round per minute.

Sixth, the decision reinforces that any change in the criminal law should be made by Congress, not by administrative agencies. The Court states: “Senator Dianne Feinstein ... 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.”

That brings us to Justice Samuel Alito’s concurrence, which stated: “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.” Since that will now be on the table, how Congress acts if it is inclined to do so really matters.

In 2017, I testified against S. 1916 (Sen. Feinstein) in the Senate Judiciary Committee. As I summarized in my written testimony:

The misnamed Automatic Gunfire Prevention Act would apply only to semiautomatics, not automatics. Its ban on any part that “functions to accelerate the rate of fire of a semiautomatic rifle” essentially bans any semiautomatic rifle, as a mere trigger adjustment for accuracy will increase the rate of fire. Since semiautomatic rifles are commonly possessed for lawful purposes, this would violate the Second Amendment. The terms are vague in violation of due process, as a person has no way to know or measure what may increase the rate of fire. “Bump-fire device” is not defined. Ten years imprisonment is imposed for mere possession without a willfulness requirement. This would be an unprecedented ban lacking a grandfather clause or an amnesty for registration.

Congress did not act in part because the proposed bills would have criminalized millions of citizens who possessed ordinary semiautomatic rifles and who had nothing to do with bump stocks. I recall Senator Feinstein responding to me that her bill was drafted by “experts.” Indeed so, as the bill would have gone much further than restricting bump stocks, and that was the sponsors’ aim.

There is another fundamental problem lurking here. As I’ve discussed elsewhere, the National Firearms Act of 1934 did not ban machineguns, and instead was thought to be an exercise of the power of Congress to tax. In Sonzinski v. U.S. (1937), the Supreme Court held that the NFA “contains no regulation other than the mere registration provisions, which are obviously supportable as in aid of a revenue purpose. On its face it is only a taxing measure....”

However, in 1986 Congress enacted 18 USC § 922(o), which banned mere possession of machineguns not possessed by the date of enactment. Because it deviated from the rest of the Gun Control Act by including no element related to interstate or foreign commerce, judges in several circuits—albeit not a majority in any case—would have held it to be unconstitutional.

One of those judges was now-Justice Alito. Dissenting in U.S. v. Rybar (3th Cir. 1996), he wrote:

Was United States v. Lopez, 514 U.S. 549 (1995), a constitutional freak? Or did it signify that the Commerce Clause still imposes some meaningful limits on congressional power?

The statutory provision challenged in this case, the portion of 18 U.S.C. § 922(o) that generally prohibits the purely intrastate possession of a machine gun, is the closest extant relative of the statute struck down in Lopez, ... which made it a federal offense knowingly to possess a firearm in a school zone. Both are criminal statutes that regulate the purely intrastate possession of firearms. Both statutes, departing from the mold of prior federal criminal statutes governing firearms possession, lack a jurisdictional element, that is, they do not require federal prosecutors to prove that the firearms were possessed in or affecting interstate commerce.... And in passing both statutes, Congress made no findings regarding the link between the intrastate activity regulated by these laws and interstate commerce.... That responsibility ... requires us to invalidate the statutory provision at issue here in its present form.

It is no secret that many lower courts resisted Lopez, just as they later resisted Heller and Bruen. What enumerated power authorizes Congress to ban mere possession of a firearm? Before § 922(o) passed in 1986, ATF Director Stephen Higgins testified to the House Judiciary Committee that of the “118,000 [machineguns] that are registered in our files ... I can count probably in less than my fingers, the number of cases in which those have been used in a crime or a crime of violence.” Not exactly a substantial, adverse effect on interstate commerce.

But that’s all water over the dam now. While the ban on new registered machineguns won’t be revisited, bills must already be in the works to ban bump stocks. Will they allow the as many as 520,000 bump stocks (ATF’s higher estimate) to be registered? And if they do, what percentage of owners would register them?

No doubt such bills will go much further than just to ban bump stocks. Senator Feinstein’s S. 1916 certainly did—it would have banned getting a match trigger job that would make the trigger lighter, and thus able to fire faster. The sponsors may also include bans on what Justice Sotomayor called “commonly available, semiautomatic rifles” like the AR-15.

Whatever the future holds, Cargill sets a good omen that the Court won’t be beholden to the administrative state and will follow Chief Justice Marshall’s words: “It is emphatically the duty of the Judicial Department to say what the law is.”