"No freeman shall be debarred the use of arms [within his own land or tenements]" -Thomas Jefferson's proposal of language to add to the Virginia Constitution
Also, there is a supreme court ruling from my home state which expresses a view of the origin of this right which goes back to England before the founding the United States:
Nunn vs Georgia (1846) "The right of the whole people, old and young, men, women, and boys, and not militia only, to keep and bear arms of every description, not such merely as are used by the militia, shall not be infringed, curtailed, or broken in upon in the smallest degree; and all this for the important end to be attained: The rearing up and qualifying a well-regulated militia, so vitally necessary to the security of a free State. Our opinion is, that any law, State or Federal, is repugnant to the Constitution, and void, which contravenes this right, originally belonging to our forefathers, trampled under foot by Charles I, and his two wicked sons and successors, re-established by the revolution of 1688, conveyed to this land of liberty by the colonists, and finally incorporated conspicuously in our own Manga Charta!"