(CN) — A 10th Circuit panel on Thursday upheld the federal government’s ban on bump stock accessories for guns, striking down a Salt Lake City resident’s challenge to the federal ban on the device that allows semiautomatic guns to fire ammunition at the same speed as automatic weapons.

After a 2017 mass shooting in Las Vegas left 58 people dead and hundreds more injured, the Justice Department and the Bureau of Alcohol, Tobacco, Firearms and Explosives issued a final rule categorizing bump stocks as machine guns, which are banned nationwide.

The move made bump-stocks illegal under the National Firearms Act and effectively banned the more than 520,000 devices already in the hands of Americans.

Under the Trump administration ban, bump-stock device owners face criminal penalties or fines if they do not turn them in or destroy them.

Salt Lake City, Utah resident W. Clark Aposhian — a gun enthusiast and the owner of a bump-stock — sued the administration in January 2019 to block the rule from going into effect.

Aposhian argued the executive branch had no authority to issue the ban and that only Congress could take such action, according to his lawsuit, which was backed by the New Civil Liberties Alliance.

After a federal judge denied Aposhian’s preliminary injunction bid, his attorneys appealed to the 10th Circuit.

In a hearing earlier this year before a panel of federal judges, an attorney for Aposhian said he purchased his bump-stock in 2014 on reliance that ATF had already approved the devices for sale.

The ATF had declared it had no power to issue rules for the devices when the federal ban was announced, Caleb Kruckenberg, a New Civil Liberties Alliance attorney representing Aposhian, told the panel. He added the devices should be regulated under the existing automatic weapon ban.

Justice Department attorneys told the panel a weapon equipped with a bump-stock qualifies as a machine gun if the device allows the gun to mimic an automatic weapon.

The 10th Circuit panel sided with the federal government Thursday, writing in a 54-page opinion that it would defer to the ATF’s reading of the law.

“The [ATF] final rule determines that semiautomatic rifles equipped with bump stocks are ‘machineguns’ because they ‘function as the result of a self-acting or self-regulating mechanism that allows the firing of multiple rounds” through “a single pull of the trigger,” U.S. Circuit Judge Mary Beck Briscoe, a Bill Clinton appointee, wrote for the panel. “Applying Chevron [deference], the statutory definition of ‘machinegun’ is ambiguous, and ATF’s interpretation is reasonable.”

The notion that bump-stock devices aren’t automatic because they won’t operate without constant forward pressure is invalid, the majority opinion states.

“The bump stock performs part of the work usually done by hand at a predetermined point in the operation, under conditions fixed for it by the shooter,” the opinion states.

U.S. Circuit Judge Nancy Moritz, an Obama appointee, joined in the majority opinion.

Kruckenberg said in a statement the ruling is disappointing and that he plans to appeal.

“Only Congress can make the law, and Congress chose not to ban bump stocks,” Kruckenberg said. “The Court allowed the ATF to take the lawmaking decision away from Congress and create brand new criminal laws in defiance of the proper constitutional order.”

The majority opinion sets a dangerous precedent on the ability of any government branch to “repair” laws it may deem ambiguous, U.S. Circuit Judge Joel Carson III, a Donald Trump appointee, wrote in the court’s dissenting opinion.

“Neither the judiciary nor the executive has the power to make or change law by creating an ambiguity where none exists,” the opinion states. “To do so (as both ATF did and the majority does today) subverts the constitutional prerogatives of each branch of government.”

Carson also took issue with the majority’s description of how a bump-stock device operates.

“Without the constant forward pressure, a nonmechanical bump stock simply will not work; the firearm to which it is attached will fire only one shot even with the stationary trigger finger applying constant backward pressure,” the opinion states. “A nonmechanical bump stock is therefore not ‘self-acting’ or ‘self-regulating.’”

The 10th Circuit had initially exempted Aposhian from the ban while it considered his motion — allowing him to continue using the device during recreational shooting — but it later reversed course.

The Justice Department did not immediately return a request for comment by press time.

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