A recent ruling by a federal appeals court struck down the Biden administration's limits on so-called "ghost guns". The court affirmed a lower court's ruling that the Bureau of Alcohol, Tobacco, Firearms and Explosives did not have the proper authority to change its rules. The ATF rule change had specified the definitions of "firearm" and other terms to regulate the production and distribution of gun parts and kits, which could be easily assembled by a consumer at home, thereby avoiding regulation and requirements for serial numbers. The court's decision was unanimous, led by Judge Kurt Engelhardt, who stated that the ATF rule "flouts clear statutory text and exceeds the legislatively-imposed limits on agency authority in the name of public policy".

https://thehill.com/regulation/court-battles/4304682-appeals-court-atf-ghost-gun-rule/