WASHINGTON (AP) — The Supreme Court seemed likely Tuesday to uphold a Biden administration regulation on ghost guns, the difficult-to-trace weapons with a rising link to crime.

In arguments that ranged to classic cars and Western omelets, key conservative justices seemed open to the government's argument that kits for quickly making nearly untraceable guns at home can be regulated like other firearms.

The manufacturers and gun rights groups challenging the rule argued the Biden administration overstepped by trying to regulate kits.

Justice Samuel Alito compared gun parts to meal ingredients, saying a lineup including eggs and peppers isn't necessarily a Western omelet. Justice Amy Coney Barrett, though, questioned whether gun kits are more like ready-to-eat meal kits that contain everything needed to make a dinner like turkey chili.

Chief Justice John Roberts seemed skeptical of the challengers' position that the kits are mostly popular with hobbyists who enjoy making their own weapons, like auto enthusiasts might rebuild a car on the weekend.

Many ghost gun kits require only the drilling of a few holes and removal of plastic tabs.

"My understanding is that it's not terribly difficult to do this," Roberts said. "He really wouldn't think he has built that gun, would he?"

A ruling is expected in the coming months.

The regulation came after the number of ghost guns seized by police around the country soared, going from fewer than 4,000 recovered by law enforcement in 2018 to nearly 20,000 in 2021, according to Justice Department data.

Finalized at the direction of President Joe Biden, the rule requires companies to treat the kits like other firearms by adding serial numbers, running background checks and verifying that buyers are 21 or older.

The number of ghost guns has since flattened out or declined in several major cities, including New York, Los Angeles, Philadelphia and Baltimore, according to court documents.

Challengers to the rule argue that most people who commit crimes use traditional guns and the Bureau of Alcohol Tobacco Firearms and Explosives overstepped its authority. "Congress is the body that gets to decide how to address any risks that might arise from a particular product," a group of more than two dozen GOP-leaning states supporting the challengers wrote in court documents.

U.S. District Judge Reed O'Connor in Texas agreed, striking down the rule in 2023. The U.S. 5th Circuit Court of Appeals largely upheld his decision.

The administration, on the other hand, argues the law allows the government to regulate weapons that "may readily be converted" to shoot. The 5th Circuit's decision would allow anyone to "buy a kit online and assemble a fully functional gun in minutes — no background check, records, or serial number required. The result would be a flood of untraceable ghost guns into our nation's communities," Solicitor General Elizabeth Prelogar wrote.

The Supreme Court sided with the Biden administration last year, allowing the regulation to go into effect by a 5-4 vote. Roberts and Barrett joined with the court's three liberal members to form the majority.