SAN FRANCISCO — A federal appeals court in San Francisco has ruled that plans for 3D-printed, self-assembled “ghost guns” can be posted online without U.S. State Department approval.

The San Francisco Chronicle says the 2-1 decision was made Tuesday by the 9th U.S. District Court of Appeals. The court overruled an injunction issued by a federal judge last year.

Authorities have concerns about the increasing popularity of ghost guns, which generally lack serial numbers that can be used to trace them.

A ghost gun was used in last week’s shootings in San Diego that killed one person and wounded four. Police Chief David Nisleit said the unserialized weapons now account for roughly one in four guns seized by San Diego.

“We’ve seen a 169% increase in unserialized, or ‘ghost guns,’ from 2020,” Nisleit told reporters after the Gaslamp Quarter shooting. “It’s very concerning. We’re seeing a lot of ghost guns. I think I reported not more than a month ago that about one in four of every gun we recover right now is a ghost gun.”

The largely untraceable weapons have taken a prominent place in recent calls for gun reform following mass shootings across the nation, and President Joe Biden took aim at the weapons in a recent series of executive orders on gun laws.

As part of Biden’s new orders, the Justice Department “will issue a proposed rule to help stop the proliferation of ‘ghost guns,’” the White House says. The rule is expected to effectively classify the kits used to build guns as firearms, making them subject to the same federal laws surrounding pre-assembled weapons, but specific details have not yet been released.

Beyond the federal regulations, California already has passed a law stating that starting in 2025, most individual gun parts will have to be sold through a licensed firearm dealer and will require a state background check. According to the Giffords Law Center, officials have agreed to speed up implementation of the policies, with most in place by 2022.