The Bureau of Alcohol, Tobacco, Firearms and Explosives states that:
The term "firearm" is defined in the Gun Control Act of 1968, 18 U.S.C. Section 921(a)(3), to include "(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...." Based on Section 921(a)(3), air guns, because they use compressed air and not an explosive to expel a projectile, do not constitute firearms under Federal law unless they are manufactured with the frames or receivers of an actual firearm. Accordingly, the domestic sale and possession of air guns is normally unregulated under the Federal firearms laws enforced by ATF.[31]