WASHINGTON (AP) — President Donald Trump is telling his Justice Department to ban rapid-fire bump stock devices like those used in last year's massacre in Las Vegas. But some officials in the department are not sure they can.

The president's surprise order this week comes as the federal Bureau of Alcohol, Tobacco, Firearms and Explosives is deep in a review of whether it has the power to regulate bump stocks without action from Congress.

Imposing any ban is likely to draw the ATF into a long legal battle with gun manufacturers.

ATF already looked at bump stocks and approved them in 2010, finding they were not the same as machine guns that are regulated under federal law.