A Utah gun rights advocate filed a lawsuit Wednesday in the United States District Court alleging that the ban on bump stocks announced last month by the Trump administration is unconstitutional.

Clark Aposhian, chairman of the Utah Shooting Sports Council, argues in the suit that the executive branch cannot rewrite laws “as it sees fit.” But he contends that’s exactly what the Department of Justice and the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) — named as defendants in the lawsuit — did to establish the new regulation.

“At its most basic, this is about constitutional order and about who has lawmaking power,” said Caleb Kruckenberg, litigation counsel for the New Civil Liberties Alliance, a nonprofit civil rights organization that is representing Aposhian in his case. “The Constitution was very deliberate. It said that Congress makes the laws through a bicameral process and then presents it to the president for signature. And that’s how we make laws and how we bind citizens to their obligations. And this turns that whole process upside down.”

President Donald Trump promised in March 2018 that he would ban bump stocks — which alter semi-automatic rifles to fire in quick bursts like a machine gun — because they “turn legal weapons into illegal machines.” To do so, his administration reclassified the accessories in December as machine guns, for which the restrictions for buying, selling or owning are heavy under federal law.

Congress has not prohibited the possession of bump stocks by statute, though it has considered at least five different bills in recent years that would have regulated the devices, the lawsuit states.

“Congress can define a machine gun any way it wants to,” said Kruckenberg, who noted that his organization has not taken a position on bump stock policy itself. “But now that it’s done so [in past legislation], the ATF doesn’t have the authority to change that and they don’t have the authority to say, ‘Well, actually it’s something very different.’”

The ban reverses an ATF decision made in 2010 and a second one under then-President Barack Obama that found bump stocks were not the same as machine guns and couldn’t be regulated the same way.

The new interpretation followed intense scrutiny on bump stocks after they were used in an October 2017 shooting at a country music concert in Las Vegas, Nevada — the worst mass shooting in modern American history, which left 58 dead and almost 100 injured.

A handful of states have since made their own rules restricting the devices, but Utah has not done so. However, a majority of residents in the overwhelmingly red state have supported outlawing the devices. In an October 2017 poll, 69 percent of surveyed Utahns, including majorities across party, ideology, religion and education-level lines, said they wanted a law prohibiting bump stocks.

But Aposhian has argued that while a bump stock makes it easier to fire rounds faster, it does not make a gun automatic. And he told The Salt Lake Tribune after the regulation was announced in December that he believes there is “no pattern of abuse or unlawful activity linked to bump stocks.”

“The one guy in Vegas certainly doesn’t constitute a pattern,” he said. “I think the president and the administration [have] let emotion rule the day on this one.”

Under the new rules, bump stock owners are required to either surrender the devices to ATF or destroy them by late March. Aposhian, who owns a bump stock, told The Tribune previously that he would turn his in during that timeframe. But his lawsuit now seeks a preliminary and permanent injunction prohibiting enforcement of the rule on him and others within the jurisdiction of the court, arguing the regulation "will make owners of the estimated 520,000 lawfully acquired bump stocks into felons.”

Aposhian also wants a judgment that the law is unenforceable and payment of his attorneys’ fees.