WASHINGTON, Dec 18 - The Trump administration said on Tuesday it had banned the high-power gun attachments used in last year's Las Vegas shooting that killed 58 people, giving the owners of "bump stocks" 90 days to turn in or destroy the devices and blocking owners from being able to register them.President Donald Trump's Republican Party typically supports gun ownership, and its members have fiercely fought off perceived threats to the U.S. Constitution's Second Amendment guaranteeing Americans the right to bear arms.His administration, though, is sidestepping any potential debate in Congress in issuing a final rule on Tuesday that adds bump stocks to a definition of machine guns written 80 years ago, during the heyday of gangsters' use of "tommy guns." The attachments use a gun's recoil to bump its trigger, enabling a semiautomatic weapon to fire hundreds of rounds per minute, which many say transforms the firearm into a machine gun.The Justice Department's regulation follows the lead of many states and retailers that imposed stricter limits on sales of guns and accessories after a deadly March shooting at a Florida high school.The Trump administration is already bracing for a lawsuit from the National Rifle Association or other gun ownership groups.On a call with reporters, senior Justice Department officials on a call said they were confident in the review of case law they conducted while writing and revising the regulation. The department received nearly 190,000 comments on its proposal for the regulation.The websites for the most well-known bump stock manufacturers, Bumpfire System and Slide Fire, displayed notifications on Tuesday that they had already ceased direct sales of the devices. RW Arms, which both manufacturers described as a leading retailer, was not immediately available to comment on the ban.While bump stocks are not widespread, they are still plentiful in the market, with high sales over the internet and in big-box stores, the officials said on the call. Walmart Inc stopped selling assault firearms and accessories in 2015. After the March shooting at Marjory Stoneman Douglas High School in Parkland, Florida, the retailer raised the minimum age for buying guns at its stores. Other retailers, including Kroger Co, have also raised the minimum buying age.