The Commonwealth of the Northern Mariana Islands is part of U.S. sovereign territory, but it bans handguns, bans importing handguns into the commonwealth and limits possession of any guns by non-citizens, including lawful permanent residents. Radich v. Guerrero (D.N.M.I. Mar. 28, 2016) holds that this violates the Second Amendment, which is applicable to the commonwealth via § 501 of the CNMI Covenant (emphasis added):
To the extent that they are not applicable of their own force, the following provisions of the Constitution of the United States will be applicable within the Northern Mariana Islands as if the Northern Mariana Islands were one of the several States: Article I, Section 9, Clauses 2, 3, and 8; Article I, Section 10, Clauses 1 and 3; Article IV, Section 1 and Section 2, Clauses 1 and 2; Amendments 1 through 9, inclusive; Amendment 13; Amendment 14, Section 1; Amendment 15; Amendment 19; and Amendment 26; provided, however, that neither trial by jury nor indictment by grand jury shall be required in any civil action or criminal prosecution based on local law, except where required by local law.
The court also strikes down the ban on importing handguns, because the ban makes handguns essentially unavailable: “In the Commonwealth, the import ban on handguns can only operate as a sales ban on a constitutionally protected product. The import ban on handguns and their ammunition is unconstitutional and violates the Covenant; Defendants will be enjoined from enforcing it.” And it agrees with the parties that, if the handgun ban is unconstitutional (as it is), it can’t be applied to lawful permanent residents any more than to citizens, since the 14th Amendment has been understood as generally prohibiting state discrimination based on citizenship (and thus, under the Commonwealth Charter, discrimination by the commonwealth).