The Administration of US President Joe Biden on Wednesday filed an appeal with the Supreme Court over a 2022 Fifth Circuit ruling on so-called “ghost guns.”

The Gun Control Act of 1968 (GCA) defines a “firearm” as “(A) any weapon (including a starter gun) which will or is designed to or may readily be converted to expel a projectile by the action of an explosive; (B) the frame or receiver of any such weapon.” In April of 2022, the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) issued a Final Order amending the definitions of “firearm” and “frame or receiver” in an attempt to regulate the increasing number of ghost guns — a term used to describe weapons-part kits that can be assembled into a firearm without registration.

The Final Order was challenged and held by the US Appeals Court for the Fifth Circuit to be an unlawful exercise of authority on the part of the ATF. The ATF, as directed by the Attorney General, has the authority to “prescribe only such rules and regulations as are necessary to carry out the provisions of this chapter.” The GCA did not provide definitions for “frame or receiver.” Because of this, the Fifth Circuit held the new definitions under the Final Order to be an unlawful exercise of authority by the ATF stating: “unless and until Congress so acts to expand or alter the language of the Gun Control Act, ATF must operate within the statutory text’s existing limits.”

The Biden administration is challenging this holding, arguing the provisions of the Final Rule “reflect the plain meaning of the relevant provisions of the [GCA]…the relevant part of the [Final] Rule reaches only weapon parts kits that may ‘readily … be completed, assembled, restored, or otherwise converted’ into a functional weapon.”

This is not the only gun control challenge in front of the Supreme Court. In November of last year, the Court heard oral arguments over a ban on firearms for people subject to domestic violence restraining orders.