"A well regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed."
The Second Amendment really is frustrating. If they'd just written "the government shall not infringe on the absolute right of individual citizens to own the weaponry of their choice", then there wouldn't be any need to debate this subject. It would be crystal clear. Unfortunately, they left things fairly murky (for our purposes).

The first clause implies that the right to arms is somehow tied to or justified by a free state's need for security... a need that can only be met through a "well regulated militia". The "well regulated militia" seems to be "the people" under arms who are necessary for maintaining the security of the "free state".

Therefore, a little background on the controversies surrounding the militia at the time the Constitution was written becomes necessary to understand the intent of the amendment.

I recently found a great article on this subject called "The Security of Free States: The Second Amendment and State Militias". LINK It's worth a read-through if you're interested in the subject, but I'll try to summarize some key points.

In the post-Revolutionary War era during which the Constitution was written, militias were raised and controlled at the state level, but were being integrated into a new federal system that also contained a standing army.

Compared to the previously existing system wherein each state's militia would be independent, the Congress was trying to create a federal system wherein Congress would have the: "power to organize, arm, and discipline the militia, leaving to the states only the power to train the militia and to officer it. The federal government could also call out the state militias under very broad circumstances, including even to enforce the laws. While power was indeed to be shared between the state and federal governments, it was apparent that compared to the previous relationship that existed, the federal government would now wield significant power over the state militias."

Now, the anti-federalist's had a number of objections to this plan, but one of the most serious was that the federal government would have control over the arming of each state's militia. That is, that the Congress would have the power to arm, or to not arm, state militia's. Since state militias were seen as a countervailing power to a centralized government with a standing army, the Congress's power to neuter the militias was a political concern. There was even talk that under the new arrangements, Congress could easily muster the militia of one state (or the standing army) and use it to enforce its will in another state, whose own militia would have been disarmed.

These were apparently the concerns that lead to the drafting of the Second Amendment. The amendment was meant to assuage anti-federalist fears that the state militias would be neutered as a balancing force. Apparently, the draft that originally made it to the Convention floor included an extra clause:

"A well regulated militia, composed of the body of the people, being the best security of a free state, the right of the people to keep and bear arms shall not be infringed; but no person religiously scrupulous shall be compelled to bear arms."

The final clause was removed because Congress decided that the issue of how to deal with conscientious objectors within the militia should be left to the states. However, its initial inclusion does reinforce the centrality of militia service to the Second Amendment's intent.

Anyway, I highly recommend that anybody interested in the subject read the article linked above because it lays out the issues of the day quite well and makes the Second Amendment more understandable.

Well, what does all this mean? Practically, not very much. Most people understand the Second Amendment as a right, but the responsibility that was implied with it... the idea that adult males and their arms would be liable for duty in a state militia with a military role... no longer exists. It is clear that the concern of some gun owners - that the people be armed as a guarantee against federal power - was a concern 'back in the day'. It's just that the anti-federalists of their day seemed to envision that the arming of the citizenry would take place within the context of a well-regulated state militia.

Something to chew on.