Attorney General Holder has sounded the alarm of the threat of 3D-printed firearms, and urged Congress to renew a law that was created in response to the (fake) concern of plastic Glocks.

Calling 3-D plastic guns an “extremely serious problem,” Attorney General Eric Holder called on Congress to renew a law that requires all firearms to be subject to metal detection.

The Undetectable Firearms Act, a law first enacted in 1988 and then reauthorized in 2003, makes it illegal to “manufacture, import, sell, ship, deliver, possess, transfer or receive” any firearm that’s undetectable by scanners. But the law is set to expire Dec. 9, unless Congress again reauthorizes it. Holder said the new technology of printing 3-D guns made of plastic means guns could potentially be smuggled onto planes, into federal buildings or at large public events.

“This is an extremely serious problem,” Holder said in a statement. “This is a very worrisome threat to law enforcement and to people who fly every day. We can’t have guns legally in circulation that are not detectable by metal detectors.”

Additionally, officials do not believe there’s a risk that street criminals will be able to mass produce guns using 3-D printing technology, as the printer required to produce a gun can cost more than $100,000 and quality varies.

“This is more for someone who wants to get into an area and perhaps be an assassin,” Richard Marianos, an official with the Bureau of Alcohol, Tobacco, Firearms and Explosives, told the Wall Street Journal. “Or they want to go to a courthouse and shoot a witness.”