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.
We caution that ATF is not charged with enforcement or oversight of the firearms laws of States or localities. To determine possible restrictions on air guns where you reside, we recommend that you contact the office of your state Attorney General, the State Police, or other State/local law enforcement authorities for further guidance.