U.S. Supreme Court justices indicated they are likely to let President Joe Biden’s administration regulate build-at-home “ghost gun” kits as firearms in a clash over a rule designed to stem a torrent of untraceable weapons.

Hearing arguments in Washington, key justices questioned a federal appeals court’s conclusion that a 2022 regulation exceeds the authority of the Bureau of Alcohol, Tobacco, Firearms and Explosives under a 1968 gun control law.

The ATF regulation subjects gun kits to the same requirements as fully assembled firearms, meaning dealers must include serial numbers, conduct background checks and keep records of transactions.

Chief Justice John Roberts said kits that have been on the market are easily convertible into functioning firearms. “My understanding is that it’s not terribly difficult for someone to do this,” he said.

The Supreme Court last year said on a 5-4 vote that the regulation could stay in effect while the legal fight went forward. Roberts and Justice Amy Coney Barrett joined the three liberals in the majority.

The new rule is being challenged by a collection of manufacturers and gun-rights supporters led by Texas resident Jennifer VanDerStok. They say the administration is trying to expand the definition of a firearm beyond what Congress intended in the 1968 Gun Control Act.

“There definitely has been a sea change by the agency here,” said the challengers’ lawyer, Peter Patterson.

But the administration’s top courtroom lawyer, Solicitor General Elizabeth Prelogar, said the regulation was a response to a proliferation of kits that include “jigs” and “templates,” tools she said speed up the process of turning parts into an operable weapon. She said manufacturers were seeking to circumvent the 56-year-old gun law.

“They’ve advertised the products, in their words, as ridiculously easy to assemble and dummy-proof,” she said, “and touted that you can go from opening the mail to have a fully functional gun in as little as 15 minutes, no serial number, background check or records required.”

The administration says almost 14,000 ghost guns were recovered by law enforcement officers and reported to ATF during a five-month period last year.Prelogar drew pushback from Justice Samuel Alito, who likened gun kits to cooking ingredients.

“I put out on a counter some eggs, some chopped-up ham, some chopped-up pepper and onions. Is that a Western omelet?” he asked.

Prelogar said those ingredients were different from gun kits because they “have well-known other uses to become something other than an omelet.”

She got help from Barrett, who hinted that gun kits might be more like a popular service for making a quick dinner.

“Would your answer change if you ordered it from HelloFresh and you got a kit and it was like turkey chili, but all of the ingredients are in the kit?” Barrett asked.

“Yes, and I think that that presses on the more apt analogy here,” Prelogar responded.

The Gun Control Act defines a “firearm” to include a weapon that “may readily be converted to expel a projectile by the action of an explosive,” as well as “the frame or receiver of any such weapon.” The frame or receiver is the part of a gun that houses the firing mechanism.

The challengers say the kits don’t come with fully assembled frames or receivers, putting them outside the law’s ambit. A kit might require the removal of plastic tabs and the drilling of holes so that pins can be inserted.

Patterson said the kits appeal to people who like to build their own firearms.

Roberts suggested he was skeptical. “Drilling a hole or two I would think doesn’t give the same sort of reward that you get from working on your car on the weekends,” he said.