White House spokesman Hogan Gidley expanded on the president's comments last night, telling reporters: "It is now illegal to own or make a wholly plastic gun of any kind - including those made on a 3D printer".
The weapons, made of the same plastic as Legos, are unrecognizable by metal detectors and are untraceable because they don't have serial numbers.
Unlike traditional firearms that can fire thousands of rounds in a lifetime, the 3D-printed guns normally last only a few rounds before they fall apart, experts say.
A Texas company's plans to post blueprints for 3D printable guns online for the public has been stopped - at least for now, according to the New Jersey attorney general. A lawyer for the company said he didn't know how many blueprints had been downloaded since then.
The arguments began in 2013 when self-styled crypto-anarchist Cody Wilson showed off the world's first 3D-printed gun. In court, they'll decide whether Defense Distributed will be banned from releasing the prints while the case continues.
Presumed US war remains begin journey home from South Korea
The process of identification could take years, according to experts. It has in the past two years quickly advanced its nuclear programme.
"Even as a strong supporter of the Second Amendment this is not right", the Alaska senator Lisa Murkowski tweeted, linking to a news story on the guns. They say the US government has failed to study the national and state security implications of the decision and violated states' rights to regulate firearms. "Federal law passed in 1988, crafted with the NRA's support, makes it unlawful to manufacture, import, sell, ship, deliver, possess, transfer, or receive an undetectable firearm", Chris W Cox, executive director of the NRA Institute for Legislative Action, said in a statement. Separately, attorneys general in 21 states urged Secretary of State Mike Pompeo and Attorney General Jeff Sessions on Monday to withdraw from the settlement with Defence Distributed, saying it "creates an imminent risk to public safety".
This morning, President Donald Trump seemed to indicate opposition to Defense Distributed's publication of the designs on Twitter.
I am thankful and relieved Judge Lasnik put a nationwide stop to the Trump Administration's unsafe decision to allow downloadable, 3D-printed ghost guns to be distributed online.
Rep. Ed Royce, R-Calif., chairman of the House Foreign Affairs Committee, said he was concerned that distribution of the blueprints could allow terrorists and worldwide criminal organizations to manufacture guns that can't be detected.
Trump tweeted that he has already spoken with the National Rifle Association about the downloadable directions the Texas company wants to provide for people to make 3D-printed guns.