Utah gun lobbyist Clark Aposhian lost his latest bid to temporarily block the Trump administration’s ban on the gun accessory known as bump stocks, but his attorneys have promised that they’ll continue fighting the case.

Gun owners last year were supposed to give up or destroy the accessory — which makes a semi-automatic weapon fire in quick bursts like a machine gun — after the federal government banned them in response to the mass shooting in Las Vegas, where 58 died. It was the most deadly mass shooting in modern U.S. history.

Aposhian filed a lawsuit last January challenging the bump stock ban, arguing that outlawing the shooting accessory was unconstitutional because it amounts to the executive branch rewriting laws, a job reserved for Congress.

He had asked a Utah federal judge to press pause on the ban while his lawsuit played out, but she ruled he did not show “a substantial likelihood of success” on the merits of his lawsuit.

The 10th Circuit Court of Appeals made a similar decision Thursday, ruling he did not show he was likely to win his case or that the ban would hurt the public’s interest.

“[T]he public has a strong interest in banning the possession and transfer of machine guns, including bump stocks,” the opinion reads. “The ban supports the safety of the public in general … and the safety of law enforcement officers and first responders.”

The New Civil Liberties Alliance, whose lawyers are representing Aposhian, said they’ll seek a review of the decision from the U.S. District Court or seek a rehearing with the 10th Circuit Court of Appeals. Because he was only seeking a temporary injunction on the ban, it means his lawsuit will still continue.

The 10th Circuit decision was a 2-1 split, with Judge Joel Carson dissenting. He wrote that he did not believe the plastic shooting accessory was properly classified as a machine gun because it is not an automatic weapon. It instead requires the shooter to apply constant forward pressure with their non-trigger hand, he wrote.

The decision in Aposhian’s case comes two months after the U.S. Supreme Court rejected an appeal of the ban. A similar challenge to the ban is set to go to trial in July in Texas, according to the Associated Press.

The federal government approved bump stocks for sales in 2010 after the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) determined it was not the same as a machine gun and couldn’t be regulated as if it was.

But that all changed after a gunman outfitted several of his firearms with bump stocks in October 2017 and sprayed bullets into a crowd at a county music concert in Last Vegas, the deadliest mass shooting in modern U.S. history.

In response, President Donald Trump said he thought the devices should be banned, and many in Congress — including members from Utah — agreed.

But Congress didn't act. Instead, the ATF did, reclassifying bump stocks as machine guns. Anyone who is still in possession of one is committing a felony.

Aposhian said last year that he filed the lawsuit not because he likes bumps stocks — he’s called it one of the “lamest” shooting accessories he owns — but because he doesn’t agree with the way the ban was put into place.