Gun Control

The 5th Circuit Says the ATF Exceeded Its Legal Authority When It Banned Bump Stocks

The decision defends the separation of powers and the rule of law against an attempt to prohibit firearm accessories by administrative fiat.


The U.S. Court of Appeals for the 5th Circuit on Friday concluded that the Trump administration exceeded its legal authority when it criminalized the sale and possession of bump stocks in 2018. While the details of the 5th Circuit's decision in Cargill v. Garland might seem arcane, at bottom it upholds the separation of powers and the rule of law. The question posed by the case is not whether prohibiting bump stocks makes sense but who has the power to make that call: the legislative branch or an administrative agency that reinterpreted the law to ban products it had previously deemed legal.

Bump stocks facilitate a rapid-firing technique in which the shooter maintains forward pressure on a semi-automatic rifle, which pushes the trigger against a stationary finger. Recoil energy then propels the rifle backward, resetting the trigger, which is repeatedly activated as long as the shooter keeps his finger in place and continues to push the weapon forward. Bump stocks were of little interest to anyone aside from manufacturers, firearm aficionados, and bureaucrats until October 2017, when a gunman used them in an attack that killed 60 people in Las Vegas.

After that massacre, the 5th Circuit notes, "public pressure to ban bump stocks was tremendous," prompting two bills aimed at doing so. But then-President Donald Trump said new legislation was not necessary because the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) could impose a ban by administrative fiat. That maneuver involved classifying rifles equipped with bump stocks as machine guns, which federal law defines as weapons that "automatically" fire more than one round "by a single function of the trigger." The definition also covers parts that convert a firearm into a machine gun.

The problem for the ATF was that a rifle equipped with a bump stock, which typically includes a slide that makes it easier for the weapon to move back and forth, does not meet that definition. Such a rifle does not fire "automatically," and it still fires just one round each time the trigger is activated. As the 5th Circuit notes, the ATF had for years conceded as much, telling manufacturers that bump stocks were legal as long as they were not "equipped with springs or other internal mechanical devices that automatically assist the shooter to engage in bump firing." The ATF took that position for more than a decade, issuing dozens of advisory letters to that effect.

After Trump demanded a ban, the ATF suddenly decided that "non-mechanical" bump stocks were illegal after all. A rule it proposed in March 2018 redefined "automatically" to include the human actions necessary to maintain bump fire: keeping the trigger finger in position while pushing the rifle forward. The ATF also redefined "a single function of the trigger" as a single pull of the trigger, which it defined to exclude bumping the trigger against a stationary finger.

Sen. Dianne Feinstein (D–Calif.), one of the legislators who wanted Congress to ban bump stocks, warned that the ATF's startling reversal was bound to provoke legal challenges:

Until today, the ATF has consistently stated that bump stocks could not be banned through regulation because they do not fall under the legal definition of a machine gun.

Now, the department has done an about face, claiming that bump stocks do fall under the legal definition of a machine gun and it can ban them through regulations. The fact that ATF said as recently as April 2017 that it lacks this authority gives the gun lobby and its allies even more reason to file a lawsuit to block the regulations.

Unbelievably, the regulation hinges on a dubious analysis claiming that bumping the trigger is not the same as pulling it. The gun lobby and manufacturers will have a field day with this reasoning….

Both Justice Department and ATF lawyers know that legislation is the only way to ban bump stocks. The law has not changed since 1986, and it must be amended to cover bump stocks and other dangerous devices like trigger cranks. Our bill does this—the regulation does not.

Although Feinstein rightly described the ATF's new reading of the law as "unbelievabl[e]," several federal judges and appeals courts have accepted it, going so far as to describe it as "the best interpretation of the statute." That is the improbable conclusion that a three-judge 5th Circuit panel reached in 2021. But after the appeals court agreed to rehear that case, 13 of 16 judges rejected the panel's analysis.

"A plain reading of the statutory language, paired with close consideration of the mechanics of a semi-automatic firearm, reveals that a bump stock is excluded from the technical definition of 'machinegun' set forth in the Gun Control Act and National Firearms Act," Judge Jennifer Walker Elrod writes in the majority opinion. And even if that were not true, Elrod says, "the rule of lenity," which requires construing an ambiguous criminal statute in a defendant's favor, would preclude the government from punishing people for owning bump stocks.

When the ATF's rule took effect in March 2019, firearm accessories that previously had been legally owned were transformed into contraband, and possessing them became a felony punishable by up to 10 years in prison and a $250,000 fine. That happened even though the law had not changed and even though the ATF's new reading of it contradicted what the agency had been saying for years. The plaintiff in this case, Michael Cargill, complied with the ATF's edict by surrendering several bump stocks to the government. But he challenged the agency's authority to issue that rule, saying it was plainly inconsistent with the statutory definition of "machinegun."

The ATF now maintains that bump fire is legally indistinguishable from automatic fire. But that technique does not require any particular accessory. In fact, Elrod notes, "it is possible to bump fire an ordinary semi-automatic rifle without any assisting device." The ATF's position therefore implies that all semi-automatic rifles are illegal machine guns. The ATF avoided that plainly untenable result by arbitrarily limiting its analysis to the products it wanted to ban.

"Nobody, not even the Government, contends that semi-automatic rifles are machineguns," Elrod writes. "That concession damns the Government's position. As Cargill recognizes, if ordinary bump firing constituted automatic fire, the Final Rule would 'convert a semiautomatic weapon into a machinegun simply by how a marksman used the weapon.' That absurd result reveals the flaw in the Government's line of reasoning."

The ATF says a "function of the trigger" requires activating it by flexing a finger. The implication is that no "function of the trigger" occurs when someone fires a gun in an unconventional way—say, by pressing the trigger with a stick. Likewise if someone fires a single round by bumping the trigger against his finger or continues doing that, with or without the aid of a bump stock. Although "pulling the trigger can sometimes begin the bump firing sequence," Elrod notes, "the process is more typically begun by pushing forward on the forebody of the firearm." According to the ATF's view, even that initial activation of the firing mechanism does not count as a function of the trigger.

"The Government contends that 'single function of the trigger' means 'a single pull of the trigger and analogous movements,'" Elrod writes. "That is, according to the Government, 'function' means 'pull.' But that argument fails on its face because a shooter still pulls the trigger of a semi-automatic weapon equipped with a non-mechanical bump stock each time he or she fires a bullet. Without a bump stock, the trigger activates because the shooter flexes his or her finger; with a bump stock, the trigger activates because the recoil of the previous shot re-engages the trigger and the shooter's maintained force on the gun's forebody bumps the trigger against the shooter's finger. This is a distinction without a difference—the end result in both cases is that the trigger is pulled."

To qualify as a machine gun, a weapon also has to fire "automatically." The parties agreed that "automatically" in this context means "self-acting" but disagreed about whether that description applies to bump firing.

"Bump firing does not maintain if all a shooter does is initially pull the trigger," Elrod notes. "Rather, to continue the firing after the shooter pulls the trigger, he or she must maintain manual, forward pressure on the barrel and manual, backward pressure on the trigger ledge."

The government noted that firing a machine gun also requires sustained human action. "After all, the Government says, to operate a traditional automatic rifle, the shooter must pull and hold the trigger to fire more than one round," Elrod writes. "That argument makes the same mistake as before: it untethers 'single function of the trigger' from 'automatically.' Restated, the statute requires that a machinegun be capable of firing automatically once the trigger performs a single function. An automatic weapon satisfies this requirement because the act of pulling and holding the trigger is one function, and that function produces more than one shot. That force must be maintained on the trigger does not change this conclusion."

At the very least, Elrod says, the ATF's reversal and the dispute about its validity show that "the National Firearms Act and Gun Control Act do not unambiguously criminalize the possession of a non-mechanical bump stock." Applying the rule of lenity in this case therefore "preserves the separation of powers 'by maintaining the legislature as the creator of crimes,'" she writes. "If ATF could change the scope of criminal liability by issuing a regulation—free from the taxing obligations of bicameralism and presentment—the Executive could wield power that our Constitution reserves to the Legislature."

In addition to exercising a power that belongs to Congress, the ATF has transformed heretofore law-abiding Americans into felons by repudiating its longstanding view of what the law requires. "As Justice Holmes framed it years ago, 'it is reasonable that a fair warning should be given to the world in language that the common world will understand, of what the law intends to do if a certain line is passed,'" Elrod writes. "We cannot say that the National Firearms Act and Gun Control Act give that fair warning that possession of a non-mechanical bump stock is a crime."

So far the Supreme Court has declined to get involved in this dispute. Now that the 5th Circuit has split with three other federal appeals courts on the legality of the ATF's ban, the justices may be more inclined to address that issue. In addition to the question of how best to read the legal definition of machine guns, these cases raise the question of whether and how to apply the Chevron doctrine, which demands judicial deference to "reasonable" agency interpretations of "ambiguous" statutes.

In 2020, when the Supreme Court declined to hear an appeal of the D.C. Circuit's ruling in favor of the ATF, Justice Neil Gorsuch, a critic of Chevron deference, emphasized the puzzle that the bump stock ban poses for Americans trying to understand and comply with federal law. "The agency used to tell everyone that bump stocks don't qualify as 'machineguns,'" Gorsuch wrote. "Now it says the opposite. The law hasn't changed, only an agency's interpretation of it."

That phenomenon, Gorsuch noted, extends beyond this particular rule. "These days it sometimes seems agencies change their statutory interpretations almost as often as elections change administrations," he wrote. "How, in all this, can ordinary citizens be expected to keep up—required not only to conform their conduct to the fairest reading of the law they might expect from a neutral judge, but forced to guess whether the statute will be declared ambiguous; to guess again whether the agency's initial interpretation of the law will be declared 'reasonable'; and to guess again whether a later and opposing agency interpretation will also be held 'reasonable'? And why should courts, charged with the independent and neutral interpretation of the laws Congress has enacted, defer to such bureaucratic pirouetting?"