WASHINGTON -- The Supreme Court on Tuesday temporarily revived the Biden administration's regulation of "ghost guns" -- kits that can be bought online and assembled into untraceable homemade firearms.
In defending the rule, a key part of President Joe Biden's broader effort to address gun violence, administration officials said such weapons had soared in popularity in recent years, particularly among criminals barred from buying ordinary guns.
The court's brief order gave no reasons, which is typical when the justices act on emergency applications. The order was provisional, leaving the regulation in place while a challenge moves forward in the courts.
The vote was 5-4, with Chief Justice John Roberts and Justice Amy Coney Barrett joining the court's three liberal members -- Justices Sonia Sotomayor, Elena Kagan and Ketanji Brown Jackson -- to form a majority.
Justices Clarence Thomas, Samuel Alito, Neil Gorsuch and Brett Kavanaugh noted dissents. Like the justices in the majority, they did not explain their reasoning.
The regulation, issued in 2022 by the Bureau of Alcohol, Tobacco, Firearms and Explosives, broadened the bureau's interpretation of the definition of "firearm" in the Gun Control Act of 1968.
The change, Solicitor General Elizabeth Prelogar wrote in the Biden administration's emergency application, was needed to respond to "the urgent public safety and law enforcement crisis posed by the exponential rise of untraceable firearms."
The new regulation did not ban the sale or possession of kits and components that can be assembled to make guns, she wrote, but it did require manufacturers and sellers to obtain licenses, mark their products with serial numbers and conduct background checks.
Gun owners, advocacy groups and companies that make or distribute the kits and components sued to challenge the regulations, saying that they were not authorized by the 1968 law.
That law defined firearms to include weapons that "may readily be converted to expel a projectile by the action of an explosive" and "the frame or receiver of any such weapon."
Judge Reed O'Connor, of U.S. District Court for the Northern District of Texas, sided with the challengers and struck down the regulation in July, saying that "a weapon parts kit is not a firearm" and "that which may become or may be converted to a functional receiver is not itself a receiver."
He added: "Even if it is true that such an interpretation creates loopholes that as a policy matter should be avoided, it is not the role of the judiciary to correct them. That is up to Congress."
A three-judge panel of the 5th U.S. Circuit Court of Appeals in New Orleans refused to stay key aspects of O'Connor's ruling.
When the Supreme Court struck down a New York gun control law last year on Second Amendment grounds, it split along familiar lines, with the six Republican appointees in the majority and the three Democratic ones in dissent. The vote in the new case revealed a different fault line, with Roberts and Barrett taking a more cautious approach than the other four conservatives.
In the government's emergency application, Prelogar asked the justices to consider an analogy.
"Every speaker of English would recognize that a tax on sales of 'bookshelves' applies to Ikea when it sells boxes of parts and the tools and instructions for assembling them into bookshelves," she wrote.
A Supreme Court brief from one set of challengers said the comparison was flawed.
"Ghost guns" are becoming increasingly popular with teenagers and those whose criminal records keep them from buying guns in the marketplace. Ghost gun sales and their use in violent crimes have spiked in recent years, law enforcement agencies say.
But Prelogar noted that ATF rules do not prohibit buying or selling the kits. Instead, the rules require complying with the same regulations that concern commercial gun sales, such as obtaining licenses, marking products with serial numbers, conducting background checks and keeping records to allow law enforcement to trace firearms used in crimes.
The two sides also differed on whether there has been a spike in homemade firearms. Prelogar wrote that there has been "an explosion of crimes involving ghost guns," pointing to a sworn statement from an ATF official.
More than 19,000 firearms without serial numbers were recovered by authorities in 2021, the official said, compared with about 1,600 in 2017. He added that in the 11 months ending in July, "a total of approximately 23,452 suspected privately made firearms were recovered at crime scenes and submitted for tracing."
Such weapons are particularly attractive to criminals and minors, Prelogar wrote, adding that they "can be made from kits and parts that are available online to anyone with a credit card and that allow anyone with basic tools and rudimentary skills (or access to internet video tutorials) to assemble a fully functional firearm in as little as 20 minutes."
The challengers' brief questioned the Biden administration's data.
"The government's alleged 'epidemic' of privately made firearms traced by the police appears to be largely an artifact of police departments changing their tracing practices in response to ATF pressure," the brief said, adding that "nothing in the government's submission demonstrates that firearms made by individuals for their own personal use are fueling an increase in crime."
The brief also objected to the phrase "ghost guns," calling it "a propaganda term that appears nowhere in federal law" and one that includes both firearms "that are manufactured lawfully by individuals and those that have their serial numbers illegally obliterated."
Gun-control groups praised the court's action.
"We call on the Fifth Circuit to do the right thing and keep this vital rule intact," David Pucino, deputy chief counsel at Giffords Law Center, said in a statement. "The challenged rule simply requires that ghost gun kits are regulated like the guns that they are."
Gun rights groups were disappointed.
"We remain optimistic that we will ultimately prevail," said Second Amendment Foundation executive director Adam Kraut. "We believe the district court's rationale, striking down the final rule, was legally sound and we look forward to defending our position on appeal."
The case is Garland v. VanDerStok.
Information for this article was contributed by Adam Liptak of The New York Times and by Robert Barnes of The Washington Post.