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.

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 to 4, with Chief Justice John G. Roberts Jr. 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 A. Alito Jr., Neil M. Gorsuch and Brett M. 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 B. 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 the Federal 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 U.S. Court of Appeals for the Fifth Circuit, in New Orleans, refused to stay key aspects of Judge O’Connor’s ruling.

In the government’s emergency application, Ms. 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.

“A better analogy would be to a ‘taco kit’ sold as a bundle by a grocery store that includes taco shells, seasoning packets, salsa and other toppings, along with a slab of raw beef,” the brief said. “No one would call the taco kit a taco. In addition to ‘assembly,’ turning it into one would require cutting or grinding and cooking the meat — and until that was done, it would be nonsensical to treat it as food and the equivalent of a taco.”

The two sides also differed about whether there has been a spike in homemade firearms.

Ms. Prelogar wrote that there has been “an explosion of crimes involving ghost guns,” pointing to a sworn statement from an A.T.F. official. More than 19,000 firearms without serial numbers were recovered by the 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, Ms. 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 A.T.F. 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.”