Because it involves guns, Cargill v. Garland has been seen by supporters and opponents alike as a Second Amendment case. That is not really correct. Rather, it presents a question of basic statutory interpretation. And in answering that question, Cargill is a triumph of textualism and separation of powers concerns over purpose-driven interpretation and legislative intent.

For the majority, the words on the paper are what matter, even if the Congress that wrote them might have done things differently. It does not matter if something walks like a duck and quacks like a duck if it doesn’t have the features that Congress used to define a duck.

On the separation of powers front, Cargill is a victory for congressional lawmaking authority. Administrative agencies such as the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) cannot step in and rewrite statutes by administrative fiat just because Congress is not acting as quickly as they might wish.


What are Bump Stocks?

Cargill concerns an effort by the ATF to ban a popular firearms accessory known as a “bump stock” through administrative action.

To shoot a semiautomatic rifle, a shooter generally uses his or her finger to pull back on the trigger. When the trigger is depressed, it releases the hammer which then strikes the firing pin which strikes a primer, igniting gunpowder in a cartridge, ultimately expelling a bullet and creating recoil. To fire a second shot, the trigger must reset, which typically means the shooter releases pressure on the trigger, allowing the trigger to move forward to reengage the hammer to restore the weapon to the ready to fire condition.

“Bump firing” is a shooting method where a shooter uses the recoil of a firearm to push the trigger forward, allowing it to reset faster and thus shoot at a higher rate of fire. Bump firing does not necessarily require any specialized equipment. At its most basic level, a shooter who uses his or her shoulder to push a rifle forward against a stationary finger rather than pulling back on the trigger is engaged in “bump” firing. People can and have used basic household items like belt loops and rubber bands to facilitate bump firing.

“Bump stocks” are more specialized firearms accessories that facilitate bump firing. Bump stocks allow the firearm, including the trigger, to slide backwards when fired, while a shooter’s finger remains stationary. When met with a force, such as a shoulder pushing forward on the stock of a rifle, a bump stock allows the firearm to slide forward and reset. It may then contact a shooter’s stationary finger and fire a subsequent round. The result is that a typical shooter can fire a semiautomatic rifle equipped with a bump stock faster than he or she could without one.  

What is a “Machinegun”?

Under the National Firearms Act and the Gun Control Act, a “machinegun” is a gun that fires “automatically, more than one shot, without manual reloading, by a single function of the trigger.” Contrary to some of the rhetoric surrounding firearms, “machineguns” are generally illegal for private citizens to possess, while semiautomatic weapons are not. This prohibition includes parts or combinations of parts designed and intended to convert a weapon into a machinegun.

“On more than 10 separate occasions over several administrations,” the ATF concluded that bump stocks were not “machineguns.” Then came the October 2017 Las Vegas mass shooting, in which a gunman using weapons equipped with bump stocks murdered 58 people and wounded hundreds more. In response to the Las Vegas mass shooting, there was “tremendous political pressure to outlaw bump stocks nationwide,” including multiple proposed pieces of congressional legislation.

Rather than waiting for congressional action, the ATF choose to unilaterally adopt a final rule in 2018 purporting to classify bump stocks as machineguns, effectively outlawing them. This effectively retroactively declared millions of Americans to be criminals based on a change in “interpretation.”

Cargill is a challenge brought by a bump stock owner to the ATF’s rule.

The Court’s Decision—Textualism and the Separation of Powers

In an opinion written by Justice Thomas, and joined by the Chief Justice and Justices Alito, Gorsuch, Kavanaugh, and Barrett, the Court held that the ATF exceeded its authority in attempting to reclassify bump stocks as “machineguns.” In doing so, the Court turned to the text of the law.

To be a “machinegun,” a weapon must fire more than one round “by a single function of the trigger” and “automatically.” For the Court, the term “function of the trigger” means the mechanical function of a trigger—not the shooter’s finger. In a standard weapon, this “means the physical movement of the trigger.”

While a bump stock makes it easier for a shooter to shoot faster, it does not change the mechanical function of the trigger. For every shot, the trigger moves backwards, releasing the hammer that strikes the firing pin causing it to strike the primer and ultimately expel the bullet. For every shot, the trigger moves forward to reset by reengaging the hammer before firing again. This makes it different from a standard automatic weapon, such as an M16, where the trigger does not reset between each shot when engaged in automatic fire but instead is bypassed after the first shot.

Because the text of the law focuses on the “function of the trigger,” the movement (or lack thereof) of a shooter’s trigger finger is immaterial. It is the mechanical action of the trigger, not shooter input, that matters under the text of the law.

Because the trigger “functions” for every shot fired by a weapon equipped with a bump stock, it is not a machinegun.

Similarly, the Court determined that a weapon equipped with a bump stock does not fire “automatically,” because it requires something more than just pulling the trigger, such as pushing forward with the shooter’s shoulder to maintain bump fire.

The dissent, written by Justice Sotomayor and joined by Justices Kagan and Jackson, takes issue with this interpretation. In effect, the dissent accuses the majority of taking an overly formalist approach to the definition of “machinegun.” For the dissent, the point of the National Firearms Act was to limit guns that shoot really fast; the how is less important than the what. In support of this, the dissent points to legislative history and to claims that a more technical interpretation renders the law ineffective.

In a concurrence, Justice Alito cuts to the heart of the dispute between the majority and the dissent: “I joined the majority 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 [the law] 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.” He went on to provide a rebuke to the ATF and a recommendation for a path forward for those who oppose bump stocks: “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.”

What does it all mean?

As Justice Alito suggests, there is nothing in Cargill that would prevent Congress from changing the National Firearms Act to further restrict bump stocks. Until and unless that happens, however, the ATF cannot do so unilaterally.

Over the last few years—and particularly under the current administration—the ATF has taken an aggressive approach to interpreting its own authority in formal rulemakings and administrative actions. Cargill may be seen as a brushback for that aggressive posture. This has potential consequences both for “machinegun” cases, which may be directly impacted by Cargill’s interpretation of “automatic” and “single function of the trigger,” and for a number of challenges to ATF regulatory action, including challenges to the ATF’s “frame or receiver” rule and the “engaged in the business” rule.

Fortunately, we will not have to wait too long to see if Cargill stands alone or reflects a broader trend of checking ATF claims of authority. On April 22, 2024, the Court granted certiorari in Garland v. VanDerStok, a case challenging the ATF’s “frame or receiver” rule as beyond the scope of the agency’s authority. A decision in VanDerStok will likely come during the Court’s next term.

Gary Lawkowski is a Partner at Dhillon Law Group. Mr. Lawkowski is on the amicus brief for the National Association for Gun Rights, Inc., the National Foundation for Gun Rights, Inc., and Rare Breed Triggers, LLC, in Cargill and represents clients in cases concerning ATF actions, including relating to the definition of “machinegun.” The views expressed here are his own and are not attributable to any client.

Note from the Editor: The Federalist Society takes no positions on particular legal and public policy matters. Any expressions of opinion are those of the author. We welcome responses to the views presented here. To join the debate, please email us at [email protected].