UNITED STATES.- They look futuristic, the type of firearms that would-be assassins use in movies: 3D-printed guns made of a hard plastic that are simple to assemble, easy to conceal and tough to trace.

The future is here. After spending years fighting the federal government for the right to do so, a Texas company was given the green light to post blueprints online showing people how to make 3D-printed guns from the comfort of their home.

Gun safety advocates and some law enforcement officials are appalled, worried that this is exactly what criminals and terrorists want: guns that can’t be flagged by metal detectors, don’t have serial numbers to trace, and don’t require the usual background checks. A coalition of gun-control groups filed an appeal Thursday in federal court seeking to block a recent Trump administration ruling allowing Cody Wilson and his company, Defense Distributed, to post blueprints online to create a 3D-printed firearm.

“There is a market for these guns and it’s not just among enthusiasts and hobbyists,” said Nick Suplina, managing director for law and policy at Everytown for Gun Safety, one of the three groups that have gone to court. “There’s a real desire and profit mode in the criminal underworld as well.”

Wilson, the founder of Defense Distributed, first published downloadable designs for a 3D-printed firearm in 2013. It was downloaded about 100,000 times until the State Department ordered him to cease, contending it violated federal export laws since some of the blueprints were downloaded by people outside the United States.

But in a reversal that stunned gun-control advocates, the State Department in late June settled its case against Wilson and agreed to allow him to resume posting the blueprints at the end of July. Wilson took to Twitter, declaring victory and proclaiming he would start back up on August 1.

Wilson did not return an email seeking comment. His attorney, Josh Blackman, a professor at the South Texas College of Law Houston, declined to comment.