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. Although the federal government does not normally regulate air guns, some state and local governments do; the Law Center to Prevent Gun Violence has compiled a list of states and selected municipalities that regulate air guns, finding that 23 states and the District of Columbia regulate air guns to some degree. Two states (New Jersey and Rhode Island) define all non-powder guns as firearms; one state (Illinois) defines certain high-power and/or large calibre non-powder guns as firearms; three states (Connecticut, Delaware and North Dakota) define non-powder guns as dangerous weapons (but not firearms). The remaining states which regulate air guns impose age restrictions on possession, use, or transfer of non-powder guns, and/or explicitly regulate possession of non-powder guns on school grounds. New York City has a restrictive municipal ordinance regulating air guns. Air guns were previously banned in San Francisco, but a state preemption statute struck down the ban, and the San Francisco District Attorney declared them legal as long as they are in compliance with state law. New York state law prohibits anyone under the age of 16 from possessing an air gun. Along with state laws, local county laws or ordinances may be relevant to users of air guns. Generally, state laws do not mention air gun laws, but local counties do. References Air guns Law-related lists Firearm laws