(Reuters) - Twenty U.S. states sued the Trump administration on Thursday to block what they called its latest effort to allow blueprints for making guns from 3-D printers to be released on the internet, threatening a proliferation of “ghost guns” that spread violence.

A 3-D printed gun in Austin, Texas, U.S. August 1, 2018. REUTERS/Kelly West

Led by Washington state and controlled primarily by Democrats, the states, along with the District of Columbia, said they sued in federal court in Seattle, after the government published final agency rules earlier in the day allowing the necessary files to be posted.

According to the states, the new rules transfer oversight of 3-D printed guns to the Commerce Department from the State Department, effectively ending Congressional oversight of the blueprints and leaving behind a loophole-filled regulatory scheme allowing their distribution “with ease.”

The blueprints can be used to create ghost guns, which can be difficult to detect even with metal detectors, and difficult to trace because they lack serial numbers.

“Ghost guns endanger every single one of us,” New York Attorney General Letitia James said in a statement. “We’re filing this lawsuit to stop the Trump Administration from further facilitating the spread of gun violence at our schools, our offices, and our places of worship.”

The State Department, the Commerce Department and the Department of Justice did not immediately respond to requests for comment.

The lawsuit followed U.S. District Judge Robert Lasnik’s decision on Nov. 12 striking down an administration effort to let the Texas nonprofit Defense Distributed publish the blueprints, as part of an earlier legal settlement.

Lasnik, who sits in Seattle, cited the State Department’s prior view that making the blueprints available could threaten foreign policy and national security by enabling terrorists and other criminals to obtain firearms.

Gun rights advocates have said fears about posting blueprints were overblown.

The lawsuit concerning Defense Distributed was filed in July 2018.

President Donald Trump, a Republican, tweeted the next day that he was looking into the public sale of 3-D guns and had spoken to the National Rifle Association. He also said the guns did not “seem to make much sense!”

The other plaintiffs in Thursday’s lawsuit are California, Colorado, Connecticut, Delaware, Hawaii, Illinois, Maine, Maryland, Massachusetts, Michigan, Minnesota, New Jersey, North Carolina, Oregon, Pennsylvania, Rhode Island, Vermont and Virginia.