The US State Department has written to the gun's designer, Defense Distributed, saying that publishing such designs, which enable anyone with a 3D printer to produce their own plastic gun, could breach arms-control regulations.
The order, however, comes after the blueprints were downloaded more than 100,000 times, and cannot prevent their further redistribution by others who have already downloaded them.
The files have been removed from the company's Defcad site, and were being hosted by the Mega online service.
Social news site Reddit has also been used to publicise existing links to the blueprints on the filesharing service Pirate Bay, which is likely to mean their further distribution is hard to prevent.
The Office of Defense Trade Controls Compliance told Defense Distributed founder Cody Wilson to ensure the designs be "removed from public access". It said he must prove he had not broken laws on shipping weapons overseas by putting the files online and letting people outside the US download them.
Mr Wilson told Forbes “We have to comply”, but claimed the State Department's fears was wrong to worry because Defense Distributed met requirements that exempted it from the arms-control regulations.
Instructions for making The Liberator, a plastic handgun that could escape detection by conventional airport security, were made freely available to download from the internet by anti-government activists in the US.
It was created by a group in Texas that aims to make “WikiWeapons” that can be reproduced with a home computer and a $1,000 (£644) 3D printer that uses heated plastics instead of ink.
“It’s a demonstration that technology will allow access to things that governments would otherwise say that you shouldn’t have access to,” Cody Wilson, the leader of Defense Distributed, told The Daily Telegraph.
“Things that there are legitimate demands for will be available,” said Mr Wilson, 25, who is described as a free-market anarchist. “That’s the point we want to make.”
Video footage showed Mr Wilson successfully test firing the gun at a target.
The Liberator, which fires .380-calibre bullets, comprises 15 printable plastic components and a single metal nail as a firing pin, which appears to be too small to trigger metal detector systems.
It was produced with a 3D printer that Mr Wilson bought on eBay for $8,000 (£5,140). The printer draws on a supply of a heated common plastic where a regular printer uses an ink cartridge.
It dispenses layer upon layer of the heated plastic to gradually build a three-dimensional solid object, as dictated by the computer design software that handles blueprints such as Mr Wilson’s.