Though the scope of the right to keep and bear arms includes self-defense and militia duty, it also involves the right of the people to resist tyranny. Many believe resistance by citizens with nothing but small arms against a tyrannical government in possession of high-tech helicopters, fighter planes, tanks, and nuclear weapons would be futile.
Recent history seems to suggest otherwise.
The arguments of earlier times may seem most remote in their insistence that private gun ownership is a necessary check on government opponents. But even on this point, the wisdom of the past should not be dismissed too quickly. James II was not induced to abandon his throne by citizen militias but by a professional army under William of Orange. Even the American colonists could not have secured their decisive victory over the British at Yorktown without extensive assistance from the professional army and the sizable navy of France. Enthusiasm for armed citizens was not, even in the seventeenth and eighteenth centuries, based on the notion that such citizens could defeat professional armies on their own.