WASHINGTON — The U.S. Supreme Court is reinstating a regulation aimed at reining in the proliferation of ghost guns, firearms without serial numbers that have been turning up at crime scenes across the nation in increasing numbers.

The court on Tuesday voted 5-4 to put on hold a ruling from a federal judge in Texas that invalidated the Biden administration’s regulation of ghost gun kits. The regulation will be in effect while the administration appeals the ruling to the 5th U.S. Circuit Court of Appeals in New Orleans — and potentially the Supreme Court.

Justices Samuel Alito, Neil Gorsuch, Brett Kavanaugh, and Clarence Thomas would have kept the regulation on hold during the appeals process.

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19,000 Ghost Guns Seized by Police

The Justice Department had told the court that local law enforcement agencies seized more than 19,000 ghost guns at crime scenes in 2021, a more than tenfold increase in just five years.

“The public-safety interests in reversing the flow of ghost guns to dangerous and otherwise prohibited persons easily outweighs the minor costs that respondents will incur,” Solicitor General Elizabeth Prelogar, the administration’s top Supreme Court lawyer, wrote in a court filing.

The new rule was issued last year and changed the definition of a firearm under federal law to include unfinished parts, like the frame of a handgun or the receiver of a long gun, so they can be tracked more easily. Those parts must be licensed and include serial numbers.

Manufacturers must also run background checks before a sale — as they do with other commercially made firearms. The requirement applies regardless of how the firearm was made, meaning it includes ghost guns made from individual parts or kits or by 3D printers.

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Gun Kits Still Allowed

The rule does not prohibit people from purchasing a kit or any type of firearm.

U.S. District Judge Reed O’Connor, in Fort Worth, Texas, struck down the rule in late June, concluding that it exceeded the Bureau of Alcohol, Tobacco, Firearms and Explosives’ authority. O’Connor wrote that the definition of a firearm in federal law does not cover all the parts of a gun. Congress could change the law, he wrote.

Lawyers for individuals, businesses, and advocacy groups challenging the rule told the Supreme Court that O’Connor was right and that the ATF had departed from more than 50 years of regulatory practice in expanding the definition of a firearm.