Sources close to GOP leaders say that if bump stocks circumvent the federal law banning the civilian sale and possession of machine guns, the matter should be left to the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF).

“Machine guns are already illegal so if this device is found to turn semi-automatics into machine guns, then there isn’t a need for Congress to act,” said one Republican senator shortly after the National Rifle Association (NRA) issued a statement Thursday calling on the ATF to review the issue.