From NPR: Justice Department to Announce “Bump stocks” are Machine Guns Officially Friday

The Trump administration is banning bump stocks, the firearm attachment that allows a semi-automatic weapon to shoot almost as fast as a machine gun. -NPR Politics

Current bump stock owners will have the 90 days before the new rule takes effect to either destroy the devices they own or turn them in to the Bureau of Alcohol, Tobacco, Firearms and Explosives.

The new regulations, which were signed by acting Attorney General Matthew Whitaker, will take effect 90 days after being published in the Federal Register. A Justice Department official said that would likely happen Friday.

The new regulations could face legal challenges from the National Rifle Association, bump stock owners or manufacturers. A Justice Department official said the department is confident in its analysis and is prepared to defend the new rule in court if needed.