Nine U.S. states launched lawsuits on Monday against the Trump administration for allowing the online distribution of the blueprint for a 3D-printed gun, warning the information could fall into the hands of criminals and terrorists.

The schematics are due to be made fully available online on August 1 by a self-described anarchist and gun advocate, Cody Wilson, who has been leading the campaign to get the information out.

President Donald Trump's administration suddenly reversed course last month and decided to settle a suit filed by Wilson, allowing him to publish the information.

The administration of Trump's predecessor, Barack Obama, had prohibited the distribution of the blueprint on security grounds.

"These downloadable guns are unregistered and very difficult to detect, even with metal detectors, and will be available to anyone regardless of age, mental health or criminal history," said Attorney General Bob Ferguson of Washington, a north-western state.

Ferguson was leading eight other states' attorneys-general who warned that the measures will allow anyone with a 3D printer to get a weapon without restrictions. They want courts to order a temporary restraining order prior to Wednesday.

A letter from 21 state attorneys-general to Secretary of State Mike Pompeo and Jeff Sessions, the federal Attorney General warned the country would be less safe if the information was legally distributed.

"In addition to helping arm terrorists and transnational criminals, the settlement and proposed rules would provide another path to gun ownership for people who are prohibited by federal and state law from possessing firearms," the letter said.