FILE PHOTO: Guns are displayed at an exhibition booth, during the annual National Rifle Association (NRA) meeting in Dallas, Texas, U.S., May 19, 2024. REUTERS/Shelby Tauber/File Photo

By Nate Raymond

(Reuters) -Fifteen Democratic-led U.S. states filed a lawsuit on Monday seeking to block Republican President Donald Trump's administration from returning thousands of previously seized devices that can be used to convert semiautomatic rifles into weapons that can shoot as quickly as machine guns.

The states filed the lawsuit in federal court in Baltimore in the wake of the administration's May 16 settlement that resolved litigation involving a ban on certain "forced-reset triggers" imposed by the government under Trump's Democratic predecessor Joe Biden. The states in the lawsuit said such devices remain illegal to possess under federal law.

The Bureau of Alcohol, Tobacco, Firearms and Explosives under Biden issued the ban after it determined that some of these devices should be classified as illegal machine guns under a federal law called the National Firearms Act.

"We will not stand by as the Trump administration attempts to secretly legalize machine guns in an effort to once again put firearms industry profits over the safety of our residents," New Jersey Attorney General Matthew Platkin said in a statement.

The lawsuit was led by New Jersey, Delaware and Maryland, and also included the states of Colorado, Hawaii, Illinois, Maine, Massachusetts, Michigan, Minnesota, Nevada, Oregon, Rhode Island, Vermont and Washington as well as the District of Columbia.

The Trump administration's settlement reversed course on the Biden administration's policies.

The settlement resolved lawsuits brought by a gun rights group challenging the ban and cases brought by Biden's Justice Department against a manufacturer of the devices. Those cases had resulted in conflicting court rulings over the legality of classifying these devices as illegal machine guns.

As part of the settlement, the Trump administration agreed to not apply the machine gun ban to such devices as long as they are not designed for use with handguns and agreed to return nearly 12,000 forced-reset triggers that had been seized by the government to their owners. The new lawsuit seeks to block the return of these devices to their owners.

The states said conversion devices like forced reset triggers have been frequently used in recent years in violent crimes and mass shootings, and that at least 100,000 such devices that were distributed nationally in recent years should be considered illegal machine guns.

The Justice Department did not immediately respond to a request for comment.

(Reporting by Nate Raymond in Boston; Editing by Will Dunham)