A "ghost gun" is kit, usually sold online, which can easily be assembled into a functioning gun, with no serial number, background check, or record keeping. The Biden administration amended federal regulations to define such kits as "firearms", effectively banning them because their entire purpose is to avoid federal firearm regulation.

The 5th Circuit last fall held that the rule banning "ghost guns" “flouts clear statutory text and exceeds the legislatively-imposed limits on agency authority in the name of public policy.” It enjoined enforcement of the rule, but the Supreme Court put that injunction on hold until the resolution of this case.

https://www.scotusblog.com/case-files/cases/garland-v-vanderstok-2/

This question resolves YES if the Supreme Court reverses the 5th circuit and allows the rule to stand. It resolves NO if the 5th circuit is upheld. In a more complex situation, it will resolve according to whether the ultimate effect results in the rule remaining in effect.