The ATF previously ruled that the devices don't fit the legal definition of "machine guns," which are illegal under federal laws, and that it could not restrict bump stocks without a new law from Congress. Manufacturers of the devices have letters from the ATF on their websites to reassure customers that the devices are legal. If the rule is made final, owners of bump stocks would be required to turn them in or destroy them, though manufacturers could sue to block enforcement.

Source: Los Angeles Times March 23, 2018 22:41 UTC