It is generally unlawful to import a machinegun into the United States for unrestricted sale. However, machineguns that are properly destroyed to ATF specifications may be imported. A machinegun parts kit is generally importable so long as the kit does not include a machinegun, barrel, frame, or receiver. Note that machinegun destruction to ATF specifications will generally render a machinegun parts kit importable in this respect (destroying a kit’s barrel, and/or frame, and/or receiver to ATF specifications so they are no longer considered a barrel, frame, or receiver will generally render the kit importable in this respect). Importations are subject to country restrictions. For example, machinegun parts kits from firearms manufactured in Russia or one of the former Soviet States are not importable. Machinegun parts kits (excluding the frame, receiver, or barrel) from a surplus military U.S. origin machinegun will also require retransfer authorization from the U.S. Department of State.
(18 U.S.C. § 922(o); 26 U.S.C. § 5844; 22 U.S.C. § 2778; 27 C.F.R. §§ 447.11, 447.21, 447.41, 447.52; ATF Rul. 2003-1, 2003-2, 2003-3, 2003-4)