A federal judge on Tuesday blocked the online publication of 3D-printed gun blueprints that lawmakers around the country feared would lead to a wave of easily produced, untraceable firearms.

US District Judge Robert Lasnik’s restraining order in Seattle effectively halted a company’s plans to release the designs, arguing, “There is a possibility of irreparable harm because of the way these guns can be made.”

The order followed President Donald Trump’s comments raising concerns about 3D-printed guns. Trump had tweeted on Tuesday morning, “I am looking into 3-D Plastic Guns being sold to the public. Already spoke to NRA, doesn’t seem to make much sense!”

Since making a 3D-printed gun only requires a 3D printer, the right materials, and a blueprint, the concern is that 3D-printed guns will make it easy to bypass a host of state and federal laws. Printing a gun doesn’t require a background check or any documentation, offering a workaround for people who are legally prohibited from buying a gun now due to, say, a criminal record or history of mental illness. A 3D-printed gun can also be easily made without a serial number or anything that would make these firearms easily traceable if they’re used in a crime.

The wide release of the 3D-printed gun blueprints, however, has only become an issue now in large part due to the Trump administration.

The previous administration, under President Barack Obama, had forced libertarian Cody Wilson to stop publishing these blueprints on his website, Defcad.com. Wilson sued the administration in hopes of republishing his schematics. The case seemed like an easy win for the government, with multiple courts initially ruling in the government’s favor.

But once the Trump administration came in, with its gun-friendly politics, the Justice Department abruptly agreed to a settlement — giving Wilson and his nonprofit, Defense Distributed, “essentially everything they wanted,” Andy Greenberg reported for Wired. The deal allowed Wilson to publish his blueprints starting in August, and paid him $40,000 for his legal costs.

The federal court, however, put Wilson’s plans on hold.

It remains unclear what happens next. Will the district court’s order survive appeals? Will the Trump administration take new action? And even if the court order holds up, how long can the government really stop 3D-printed guns from becoming mainstream — given that the internet has, from piracy to blueprints for other kinds of weapons, always found a way to quickly spread information?

In fact, there already are websites hosting 3D printer designs for guns, and sites dedicated to hosting Wilson’s files, even as Wilson’s own ability to republish the documents is held up in court.

For more about the battle to stop 3D-printed guns, read Vox’s explainer.