This article has been updated to reflect an updated statement from the Bureau of Alcohol, Tobacco, Firearms and Explosives.

AUSTIN (Nexstar) — A Texas gun owner who sued the federal government over its bump stock ban argued his case in federal court Wednesday.

Michael Cargill, of Austin, sued the U.S. Department of Justice (DOJ) and the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) in 2019, claiming the government violated his rights when he was ordered to “destroy or surrender his device or face criminal prosecution,” his suit stated.

Cargill, who owns Central Texas Gun Works in Austin, appeared with his attorneys in front of Senior U.S. District Judge David Ezra in the U.S. District Court for the Western District of Texas on Wednesday morning. Lawyers from the DOJ and ATF represented the federal government.

Cargill claims that Congress has the rule-making power to ban bump stocks, and the DOJ and ATF “can’t just assume the power to rewrite the law, or our constitutional system and separation of powers with checks and balances will be gone.”

He believes the ATF’s rule violates the Constitution.

Congress has banned machine guns, though it has not banned bump stocks — a device that when installed allows a semi-automatic to fire at a rapid rate, much like a fully automatic gun.

The ATF issued a rule in Dec. 2018, amending the definition of machine gun, and requiring possessors “to destroy the devices or abandon them at an ATF office prior to the effective date of the rule.”

That rule took effect March 26, 2019.

Cargill surrendered his bump stocks, which he says he purchased lawfully, to the Austin field ATF office on March 25, 2019, the same day he filed the lawsuit.

“It doesn’t matter whether you’re a Republican, you’re a Democrat, you’re a Libertarian. It’s the fact that the federal government — an agency — actually walks into your house and says, ‘There’s something that you own, that you possess, that you legally purchased, it is now illegal. It’s banned. If you keep it, you’re a felon and we’re not going to reimburse you for it,” Cargill said Wednesday.

“The agency within the federal government does not have that power,” Cargill said.

The ATF estimated in its 2018 rule that as many as 520,000 bump stock devices could have been produced between 2010-17. The bureau estimated that between 2011-17, the total amount spent on bump-stock type devices was $102.5 million.

Representing Cargill, the New Civil Liberties Alliance, a nonprofit civil rights organization, has explained the scope of the lawsuit is not about whether or not bump stocks should be outlawed, but rather, which governmental body should be changing the law.

“This is the first opportunity in the country to have a trial to decide whether or not the bump stock rule was valid,” said Caleb Kruckenberg, litigation counsel for New Civil Liberties Alliance.

“This agency explicitly said that this device was approved. It was legally approved before Michael purchased it, and then after he owned it, they came and took it away and said that it’s now illegal,” said Mark Chenoweth, the alliance’s executive director and general counsel.

April Langwell, chief of ATF’s public affairs division, stated in an email on Wednesday that “ATF cannot provide comment on matters in litigation.”

The bump stock ban came after a shooter killed 58 people at a Las Vegas concert in 2017, a spree during which authorities believe bump stocks were used.

The next step in Cargill’s case involves both sides submitting written legal arguments to the judge by Oct. 1. He will likely render a judgement in the following months.

Russell Falcon contributed to this report.