In a separate move, 21 state attorneys general called on Pompeo and U.S. Attorney General Jeff Sessions to back out of their settlement with the company.
The company behind the plans, Austin, Texas-based Defense Distributed, had reached a settlement with the federal government in June that allows it to make the plans for the guns available for download on Wednesday. Jonathan Lowy of the Brady Center to Prevent Gun Violence told AFP that if Wilson's website is ultimately allowed to publish, the consequences could be even greater outside of the US.
Seized plastic handguns which were created using 3D printing technology are displayed at Kanagawa police station in Yokohama, south of Tokyo, May 8, 2014.
Wilson sued the federal government in 2015. Defense Distributed planned to release the instructions August 1, which is why Ferguson sought immediate relief from the court.
On Monday Ferguson announced that Washington will lead a multistate lawsuit going after the Trump administration over the settlement. The petition for the temporary restraining order was filed in federal court in Seattle. Iowa and Virginia joined the case on Tuesday.
Hours before the restraining order was issued, Democrats sounded the alarm, warning about "ghost guns" that could avoid detection and posed a deadly hazard.
"Wilson agrees not to post any new unsafe 3D printable guns until our September hearing", Grewal posted. The governor called the impending release "reckless".
The 3D-blueprints were removed from the site in 2013 because the government said it violated worldwide regulation laws, but eventually surrendered, concluding 3D-gun blueprints count as constitutionally protected speech.
The law prohibits guns that don't contain enough metal to trigger screening machines commonly found in airports, courthouses and other secure areas accessible to the public.
The weapons, he said, "could be printed anywhere in the world and, therefore, it can give national security apparatuses a great, great headache because they can't detect them".
"Until the president agrees to reverse this policy and prohibit the online publication of these risky blueprints, a decision that is entirely within his authority, I intend to place a hold on your nomination", Mr. Markey told Mr. Cooper.
Defense Distributed's files include 3-D printable blueprints for components that would go into the making of a version of the AR-15 semi-automatic assault rifle, a weapon that has been used in many US mass shootings.
Another gun made by a 3D printer.
He said it was a case of free speech and not about guns.
Critics generally say easily printable guns could allow people to circumvent federal, state, and local gun restrictions by home printing their own weapons with little oversight.
"Regardless of what a person may be able to publish on the internet, undetectable plastic guns have been illegal for 30 years".
At the time, the NRA voiced its opposition to expanding the Undetectable Firearms Act.
Last week, attorneys general from Pennsylvania, New Jersey, and the city of Los Angeles also threatened legal action against Defense Distributed in an effort to ban access to Wilson's website in their local jurisdictions.