The US government has demanded the removal of online files which allow users to 3D-print their own unregistered gun at home.
The blueprint has so far been downloaded more than 100,000 times since Defense Distributed - which spent a year designing the “Liberator” handgun - made it available online.
Last week Defense Distributed built the gun from plastic on an industrial 3D printer bought on eBay for $8,000 (£5,140), and fired it.
The Office of Defense Trade Controls Compliance wrote to the company's founder Cody Wilson demanding the designs be "removed from public access" until he could prove he had not broken laws governing shipping weapons overseas.
"We have to comply," Mr Wilson told news magazine Forbes in an interview.
But he said Defense Distributed had been set up specifically to meet requirements that exempted it from the regulations.
The designs have since been removed from the company's Defcad site, but this may not prevent people accessing the blueprints, many links to which have been uploaded to file-sharing site the Pirate Bay, making them widely available.
Wilson - a self-described "crypto-anarchist" who believes everyone has a right to a gun - welcomed the government intervention, saying it would highlight the issue of whether it was possible to stop the spread of 3D-printed weapons.
The group’s website currently has a red banner at the top reading: “DEFCAD files are being removed from public access at the request of the US Department of Defense Trade Controls. Until further notice, the United States government claims control of the information.”
Wilson told the tech blog Betabeat: “We got an official letter from the Secretary of State, telling me who they were, what their authority was under US law and telling me they want to review these files to see if they’re class one munitions. That includes blueprints.”