Some things are Self-Explanatory....

"The right [to bear arms] is general. It may be supposed from the phraseology of this provision that the right to keep and bear arms was only guaranteed to the militia; but this would be an interpretation not warranted by the intent. The militia, as has been explained elsewhere, consists of those persons who, under the laws, are liable to the performance of military duty, and are officered and enrolled for service when called upon.... [I]f the right were limited to those enrolled, the purpose of the guarantee might be defeated altogether by the action or the neglect to act of the government it was meant to hold in check. The meaning of the provision undoubtedly is, that the people, from whom the militia must be taken, shall have the right to keep and bear arms, and they need no permission or regulation of law for the purpose. But this enables the government to have a well regulated militia; for to bear arms implies something more than mere keeping; it implies the learning to handle and use them in a way that makes those who keep them ready for their efficient use; in other words, it implies the right to meet for voluntary discipline in arms, observing in so doing the laws of public order."

- Thomas M. Cooley, General Principles of Constitutional Law, Third Edition [1898]