The ATF’s bump stock ban doesn’t square with federal law and can’t stand.

That’s the ruling handed down by an en banc panel of the Fifth Circuit Court of Appeals on Friday. By a vote of 13-3, the full court overturned a December 2021 panel ruling in favor of the ban. It found the Trump-era rule created by the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) in response to the Las Vegas shooting violates the Administrative Procedure Act because it goes against the plain meaning of the federal laws it was purporting to enforce.

“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 wrote for the majority in Cargill v. Garland.

While it doesn’t deal directly with the Second Amendment, the ruling is a significant win for gun-rights activists who’ve fought the ban since it was enacted in 2018. It sets up a potential Supreme Court showdown because other appeals courts have previously upheld the regulation. Friday’s ruling creates the first new circuit split over a gun law since the Court’s landmark June 2022 decision in New York State Rifle and Pistol Association v. Bruen, which set a higher standard for reviewing gun restrictions.

The ban targets specialized stocks that are designed to replace traditional stocks in order to help facilitate bump firing. That method uses a gun’s recoil to enable a shooter to depress the trigger on a semi-automatic firearm much more quickly than by pulling it in a traditional manner. When bump firing a shooter holds their finger in a fixed position and pushes forward with the firearm causing the round to fire and allowing the shot’s recoil to move the gun far enough rearward to reset the trigger before it is pushed back into the shooter’s finger.

Bump stocks make the method easier to achieve by allowing the grip and stock to slide independently of the rest of the gun. However, bump firing is possible on any semi-automatic firearm without using specialized stocks or any other accessory.

The technique allows the shooter to achieve a much higher rate of fire. But it also requires the trigger to be actuated for every individual shot unlike a fully-automatic machinegun, which will continually fire after a single trigger pull until its ammunition is depleted or the trigger is released. The Fifth Circuit ruled these are key distinctions that mean a bump stock can’t be classified as a machinegun (effectively banning them) under current federal law.

“Bump firing does not maintain if all a shooter does is initially pull the trigger,” the court found. “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.”

That means bump stocks are by definition not machineguns under the National Firearms Act and are not subject to the registration and tax requirements under the law. The ATF had tried to use the registration requirement to ban the devices since the machinegun registry has been closed since 1986, which made it impossible to legally register, and therefore possess, bump stocks under the agency’s rule.

The Fifth Circuit ruled the process the ATF used usurped the powers of Congress.

“As an initial matter, it purports to allow ATF—rather than Congress—to set forth the scope of criminal prohibitions,” Elrod wrote. “Indeed, the Government would outlaw bump stocks by administrative fiat even though the very same agency routinely interpreted the ban on machineguns as not applying to the type of bump stocks at issue here. Nor can we say that the statutory definition unambiguously supports the Government’s interpretation.”

The majority further condemned the ATF’s reasoning because it could be used to justify declaring all semi-automatic firearms machineguns.

“We reiterate that a shooter can bump fire an ordinary semi-automatic rifle even without a bump stock,” Elrod wrote. “But nobody, not even the Government, contends that semi-automatic rifles are machineguns. That concession damns the Government’s position.”

Judge Stephen Higginson, joined by judges James Dennis and Graves, dissented. They disagreed with the court’s contention that bump stocks don’t meet the definition of a machinegun under federal law or even that the definition is ambiguous about it. They accused their colleagues of “legaliz[ing] an instrument of mass murder.”

“Today, our court extends lenity, once a rule of last resort, to rewrite a vital public safety statute banning machineguns since 1934,” Higgenson wrote. “In conflict with three other courts of appeals, our court employs its new lenity regime to carve out from federal firearms regulation the bump stock—a device that helped the Las Vegas shooter fire over a thousand rounds during an eleven-minute long attack, at times shooting about nine bullets per second, killing at least 58 people and wounding hundreds more.”

The rest of the court said what matters is how Congress wrote the law that governs machineguns, whether the judges like the definition or not.

“Prudent or not, Congress defined the term “machinegun” by reference to the trigger’s mechanics,” Elrod wrote for the majority. “We are bound to apply that definition as written.”

The majority argued there was no escaping the conclusion that the ATF’s rule can’t stand.

“The definition of ‘machinegun’ as set forth in the National Firearms Act and Gun Control Act does not apply to bump stocks,” Elrod wrote. “And if there were any doubt as to this conclusion, we conclude that the statutory definition is ambiguous, at the very least. The rule of lenity therefore compels us to construe the statute in Cargill’s favor.”

The Fifth Circuit remanded the case back down to the district court. It ordered the lower court to rule in favor of Cargill and determine the proper scope of relief.

The Department of Justice did not respond to a request for comment on whether it planned to appeal the decision.

UPDATE 1-6-2023 9:33 PM EASTERN: This piece has been updated with more details from the ruling.