By 5-4 Vote, Supreme Court Revives Biden’s Regulation of ‘Ghost Guns’

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 on whether there has been a spike in homemade firearms.

Ms. Prelogar wrote that there had 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.”