Bump stock owners filed the $500,000 lawsuit in March, after a federal reclassification of bump stocks as machine guns effectively outlawed their possession.
"These dangerous regulations can go much farther than just bump stocks," Erich Pratt, executive director of Gun Owners of America, said.
The Department of Justice submitted notice of proposed regulation to clarify the meaning of "machinegun" in the National Firearms Act and Gun Control Act includes bump stock devices, and that federal law, therefore, prohibits their possession, sale, or manufacture.
Bump stocks were used by Las Vegas shooter Stephen Paddock to kill 58 people before he committed suicide.
Wayne LaPierre said Hollywood was teaching gun irresponsibility to the American public.
Hundreds of thousands of people flock to Lollapalooza each year, including the elder daughter of former President Obama in August.