FILE PHOTO: A bump fire stock that attaches to a semi-automatic rifle to increase the firing rate is seen at Good Guys Gun Shop in Orem, Utah, U.S., October 4, 2017. REUTERS/George Frey/File Photo

WASHINGTON (Reuters) - A U.S. appeals court on Monday refused to halt President Donald Trump’s ban on “bump stocks” - rapid-fire gun attachments used in the deadliest mass shooting in modern U.S. history - in the latest courtroom defeat for firearms rights advocates opposing the policy.

The U.S. Court of Appeals for the District of Columbia Circuit upheld a lower court ruling that denied a request by opponents of the policy for a preliminary injunction lifting the ban, which took effect last week. The U.S. Supreme Court twice last week, in cases from Michigan and Washington, D.C., rejected stay requests from gun rights advocates.

The policy was embraced by Trump in the wake of an October 2017 mass shooting that killed 58 people at a country music festival in Las Vegas. It requires owners to turn in or destroy the attachments. People caught in possession of them could face up to 10 years in prison.

The appeals court previously carved out a temporary exception to the ban for members of the Firearms Policy Foundation and other organizations pursuing the legal challenge. In Monday’s decision, the court said it would extend that temporary reprieve for two days to allow the plaintiffs to seek a stay from the U.S. Supreme Court.

“We are reviewing the decision and will be seeking a stay from the Supreme Court, within the time contemplated by the D.C. Circuit,” said Erik Jaffe, a lawyer for the plaintiffs.

Bump stocks use a gun’s recoil to bump its trigger, enabling a semiautomatic weapon to fire hundreds of rounds per minute, which can transform it into a machine gun. The ban is a rare recent instance of gun control at the federal level in a country that has experienced a succession of mass shootings.

Those challenging the policy have argued that the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) lacks the authority to equate bump stocks with machine guns. One of the laws at the center of the legal dispute was written more than 80 years ago, when Congress restricted access to machine guns during the heyday of American gangsters’ use of “tommy guns.”

The appeals court, in its 2-1 ruling, said in Monday’s decision that gun rights activists had failed to show that ATF acted unreasonably when it reinterpreted the language to include bump stocks. The judge who dissented in the ruling, Judge Karen LeCraft Henderson, said that “the plaintiffs are likely to succeed on the merits of their challenge and I would grant them preliminary injunctive relief.”