Although the phrase implies that the carrying of the weapon is for the purpose of “offensive or defensive action,” it in no way connotes participation in a structured military organization.

From our review of founding-era sources, we conclude that this natural meaning was also the meaning that “bear arms” had in the 18th century. In numerous instances, “bear arms” was unambiguously used to refer to the carrying of weapons outside of an organized militia. The most prominent examples are those most relevant to the Second Amendment: Nine state constitutional provisions written in the 18th century or the first two decades of the 19th, which enshrined a right of citizens to “bear arms in defense of themselves and the state” or “bear arms in defense of himself and the state.” It is clear from those formulations that “bear arms” did not refer only to carrying a weapon in an organized military unit. Justice James Wilson interpreted the Pennsylvania Constitution’s arms-bearing right, for example, as a recognition of the natural right of defense “of one’s person or house”—what he called the law of “self preservation.”

Justice Antonin Scalia, District of Columbia v. Heller. 2008.