The US Department of Justice said it obtained a court order blocking two firearms companies from imperiling public safety by illegally selling devices to convert AR-15-type rifles into machine guns.
US District Judge Nina Morrison in Brooklyn on Wednesday issued a temporary restraining order against Florida-based Rare Breed Triggers LLC and Rare Breed Firearms LLC, and their owners.
The Justice Department said the defendants have sold thousands of devices known as FRT-15s, that are designed and intended to convert AR-15-style semiautomatic firearms into machine guns.
It said those devices are therefore classified as machine guns under federal law, and did not qualify for the limited exceptions permitting their sale.
The defendants were not immediately available for comment.
Attorney General Merrick Garland said the Justice Department will do "everything in its power to protect the American people from gun violence and to hold accountable those that flood our communities with illegal guns."
A federal civil complaint made public on Thursday accused the Rare Breed defendants of mail fraud, wire fraud and conspiring to defraud the United States.
It seeks to ban FRT-15 sales, and recover previously sold devices with refunds going to buyers.