A small company operating out of a warehouse on the edge of a sagebrush airstrip near Carson City, Nev., temporarily halted its operations this summer, which gun control groups hailed as a major victory in their fight to stem the spread of unregulated firearms in America.

The company, Polymer80, was for a time the country’s largest manufacturer and online seller of the components used to assemble the untraceable homemade weapons known as “ghost guns.” The weapons fueled a surge in gun crime after the onset of the coronavirus pandemic across the country, particularly in California, according to law enforcement officials.

Hit by a wave of lawsuits, the company also struggled to cope with new regulations imposed by the Biden administration that restricted the sale of the components. In July, Polymer80’s embattled owner announced on social media, “we are shut down… for now” to evaluate the feasibility of his business model.

On Tuesday, the Supreme Court will consider a challenge, brought by gun rights groups and supported by industry leaders, that seeks to invalidate the Biden administration rules, which are from the Bureau of Alcohol, Tobacco, Firearms and Explosives. Those rules, completed in late 2022, require vendors who sell partly finished frames of Glock-style handguns — the pistol grip and firing mechanism — to treat them like fully completed firearms subject to federal regulations.

The case has profound implications: The number of ghost guns recovered at crime scenes has fallen since the enactment of the rules, which mandated the use of serial numbers and required buyers to undergo background checks, according to statistics compiled by law enforcement agencies around the country.

Local officials and gun control groups fear that overturning the restrictions could reverse the recent improvements. They also say it could pave the way for a sweeping expansion of a business they say offers untraceable weapons to those banned under federal law from possessing them: criminals, people with histories of mental illness and teenagers, the victims and perpetrators of some of the most horrific crimes involving ghost guns.

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