UPDATE 1-U.S. appeals court refuses to block 'bump stocks' gun ban

A U.S. appeals court on Monday said it would not 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 in a string of courtroom defeats 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, embraced by Trump in the wake of an October 2017 massacre in Las Vegas in which bump stocks were used, requires owners to turn in or destroy the attachments, and 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 48 hours to allow the plaintiffs to seek a stay from the U.S. Supreme Court.

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. (Reporting by Jan Wolfe, Editing by Will Dunham and Franklin Paul)