David Young on the "Mason Triad"
David E. Young has an interesting post on the Mason Triads, a term he invented to describe the triple provision often found in early constitutions, starting with the Virginia one -- (1) either praise of the militia, or a right to bear arms; (2) restrictions on, or at least discouragement of, standing armies in time of peace; and (3) recognition of civilian control of the military. As he notes, Madison could omit the last two since the Constitution itself ensured civilian control, and legislative control over the military. All that remained was to implement (1), by ensuring that the civilian populace would be armed.
"...its purpose was to assure the people's control over the new Federal Government they authorized and any forces it might raise. This information fully explains the Second Amendment's references to a free state and the necessity of an effective militia of the people, who would be able to self-embody for organized defense with their own arms, because their right to possess and use arms was protected against any meddling by the government. "