The Supreme Court upheld a Biden-era regulation cracking down on so-called ghost guns Wednesday by requiring them to have serial numbers while would-be purchasers are subject to background checks and age verification.

Justice Neil Gorsuch penned the 7–2 decision, a rare setback for gun rights groups before the high court, with fellow conservative Justices Clarence Thomas and Samuel Alito dissenting.

“If Congress had wanted to regulate only operable firearms, it could have simply addressed ‘weapons’ that can ‘expel a projectile by the action of an explosive.’ But Congress didn’t stop there,” Gorsuch wrote. “Instead, Congress explained that a ‘weapon’ also qualifies for regulation if it is either ‘designed’ to accomplish that function or capable of being ‘readily … converted’ to do so.”

The Biden administration had used the Gun Control Act of 1968 to apply more stringent regulations against ghost gun kits, which allow for easy assembly of a firearm that the feds struggle to trace. 

Gun rights groups had sued on behalf of Jennifer VanDerStok and Michael Andren, two citizens who had bought those kits and wanted the right to build full-fledged guns out of them, arguing the executive branch had overstepped its boundaries and a new law was required. 

The federal Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) had drafted a regulation in 2022 that requires manufacturers and distributors of gun kits to add serial numbers, ensure that purchasers are 21 years or older and conduct background checks in keeping with the Gun Control Act.

Gorsuch underscored that the case before the high court was whether the ATF rule was “facially” or obviously inconsistent with the law, not whether “particular weapon parts kits or unfinished frames or receivers” could be subject to the rules. 

The justice attached images of a weapons kit from now-defunct manufacturer Polymer80 to his majority opinion while arguing that the purpose of the kits was obvious.

“No one would confuse the semiautomatic pistol pictured above with a tool or a toy,” he explained. “Of course, as sold, the kit requires some assembly. But a number of considerations persuade us that, even as sold, the ‘Buy Build Shoot’ kit qualifies as a ‘weapon.'”

“Even as sold, the kit comes with all necessary components, and its intended function as [an] instrument of combat is obvious.”

During oral arguments in October, an attorney for the plaintiffs argued that the gun kits may not necessarily “readily be converted” into full-fledged firearms and that there should be a “critical machining” test for such a regulation to go into effect. 

Thomas penned the dissent and accused the majority of interpreting the Gun Control Act too broadly. 

“The Government now asks us to rewrite statutory text so that it can regulate weapon-parts kits. This time, the Court obliges. I would not,” he bluntly wrote. “The statutory terms ‘frame’ and ‘receiver’ do not cover the unfinished frames and receivers contained in weapon-parts kits, and weapon-parts kits themselves do not meet the statutory definition of ‘firearm.’ That should end the case.”

The text of the Gun Control Act refers to “any weapon…which will or is designed to or 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.”

Thomas argued that “may readily be converted” could not cover ghost gun kits, which he said are “not a weapon until it is converted into an operable gun … The operable gun pictured in the majority opinion is ‘an instrument’ one may use in ‘combat.’ The unfinished, inoperable kit pieces are not.”

“ATF recognized as much just a few years ago, explaining that ‘the ‘designed to’ and ‘readily be converted’ language are only present in the first clause of the statutory definition,” the senior justice argued. “Therefore, an unfinished frame or receiver does not meet the statutory definition of ‘firearm’ simply because it is ‘designed to’ or ‘can readily be converted into’ a frame or receiver.”

A pair of lower courts, including the New Orleans-based Fifth Circuit Court of Appeals had sided with VanDerStok and Andren, ruling the 2022 ATF regulation should be quashed.

In 2018, authorities had collected 4,000 ghost guns, but by 2021, they had confiscated 20,000, according to Justice Department data. Just under 700 homicides have been tied to those weapons.

Pro-Second Amendment groups have had a long run of success before the Supreme Court, which in 2022 struck down New York’s requirements to obtain a concealed carry permit as overly onerous and last year reversed a Trump-era ban on bump stocks, enhancements that enable a semi-automatic weapon to unleash multiple rounds with a single trigger pull.