Many U.S. states have been making progress against gun violence, passing laws that make it harder for the most dangerous people to get firearms. Those gains are in jeopardy, thanks to new technology and Washington’s failure to grapple with its implications.

Last month, the State Department quietly settled a lawsuit brought by a gun entrepreneur who promotes the private manufacture of untraceable firearms. Cody Wilson, the founder of Defense Distributed, had been barred from publishing online computer files that can be used with a 3-D printer to create firearms. The State Department had imposed the ban using its export-control powers. The settlement allows Wilson to go ahead.

The legal issues are complicated. First Amendment issues arise regarding computer code. But the problem this poses is simple. The digital “speech” distributed by Wilson consists of instructions to a machine to produce a deadly weapon. His firm also markets the “Ghost Gunner 2,” a computer-controlled milling machine that manufactures gun parts. If this is permitted, people banned from possessing firearms (felons, domestic abusers, teens, the dangerously mentally ill) could make their own guns at home — lacking serial numbers, and untraceable.

Some private gunsmiths already legally manufacture guns without serial numbers. But the process demands expertise, so it hasn’t presented a public safety crisis. Technology like Wilson’s would change this radically. Indeed, it’s meant to.

This nonsensical void in the law already poses a threat, but innovators like Wilson increase that threat exponentially. It’s possible that further legal action will keep the common-sense prohibition on Wilson’s 3-D gun plans, now set to expire by August, in place.

Regardless, Congress needs to step forward with legislation. It needs to demand background checks for the components purchased to make firearms. And all guns should be traceable.

In addition, the particular threat posed by plastic guns — namely, that they’re hard to detect — needs to be addressed. Defense Distributed includes a small amount of metal in its blueprint, to comply with the 1988 Undetectable Firearms Act. But that metal piece can be removed. (In 2013, journalists smuggled a 3-D-printed plastic gun into Israel’s parliament.) A stronger requirement to make such weapons detectable will be needed.

Failure to recognize the danger posed by 3-D printing of guns will have consequences. Anonymous manufacturers will make guns designed to evade security; criminals will easily obtain firearms they aren’t allowed to buy; and law-enforcement agents will struggle in vain to trace weapons used in crimes. The Wilson settlement must not go forward.

FROM AN EDITORIAL ON BLOOMBERG VIEW