The 2nd Amendment to the U.S. Constitution has been contentious for longer than I've been alive. The amendment itself reads as follows:

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.

There are two common but different ways to interpret this:

1) U.S. citizens have the right to own and use guns; or

2) U.S. citizens who are members of a well regulated militia such as the National Guard have the right to own guns.

Neither of these interpretations is exactly what the amendment says. For example, most people think of the amendment as referring to guns. But the term used is "to keep and bear arms," which is a much more general phrase referring to weapons and soldiery. So, a strict reading of the amendment (by either interpretation) suggests that at least some citizens have the constitutional right to own knives, swords, guns, howitzers, and even thermonuclear explosives.

Since nobody is seriously suggesting issuing concealed-carry permits for suitcase nukes, the question is not whether ownership and use of arms is restricted, but how much said ownership and use is restricted, and under which circumstances the government can't refuse the right to "keep and bear arms."

Different Lives, Different Problems
Part of the problem is that the United States is a very different place than when the second amendment was written. Back in the late 1700's, the most advanced weapons were things like muzzle-loading rifles, and cannons. These were much less deadly to the target than modern weapons, and much more dangerous for the user. Nobody could have even conceived of, for example, a device--small enough to be carried on an ox-cart--which could destroy an entire city in an instant.

In addition, where the population today is overwhelmingly concentrated in large urban areas, back then the vast majority of people lived on farms or in small towns. Even if you did detonate a bomb in a major city, the impact on the population as a whole would have been much less than it would be today.

But perhaps the most interesting difference is that where today we have professional armed forces, in the post-Revolutionary War period, the army was the people. Not all of the people, of course, but the Revolutionary War was largely fought (on the U.S. side, excepting the foreign aid) by ordinary people who took up arms against the king. The last time we had anything even approaching that sort of mass citizen-soldiery was in World War II, when an entire generation of young men was inducted into the armed forces to fight Hitler.

Looking at the 2nd amendment in the context of the citizen army of the Revolutionary War, it is just as easy to add a third interpretation:

3) U.S. citizens have the right to join the armed forces.

This interpretation makes a lot of sense in the historical context of the Revolutionary War. It prevents the government from, in essence, creating an army of foreign mercenaries without any U.S. citizens. Given that the British used Hessian mercenaries and (largely non-colonial) British soldiers against the U.S. in the war, the Founding Fathers would have been rightly concerned that a Federal government might raise a foreign army in order to dominate the individual states. Fortunately, the concept of civilian control over the military is now so deeply ingrained in our system, this risk seems exceptionally remote today.

But the real point is....
This is a very circular way of making my fundamental point, which is that the arguments over gun control are really misplaced. In the U.S., most debates seem to center on the meaning and intent of the second amendment. Unfortunately, the amendment can be interpreted in any number of ways, including some which might have made sense in the 1780s, but which are absurd now (for example, that "arms" means any kind of weapon). With this kind of ambiguity, any argument about the meaning of the constitution can literally never be resolved.

Of course, if you make your living lobbying congress about any issue, it is in your best interest that the issue not get resolved.

The real debate should be over the underlying policy. Both sides of the debate have staked out some fairly extreme positions, and any real resolution needs to start by conceding some points.

Points Which Gun Control Advocates Should Concede:
1) Most gun owners are not raving lunatics bent upon mass destruction.

2) Responsible target shooting and hunting are acceptable activities, even if you personally don't care for them.

3) There are circumstances when carrying a gun for personal protection is appropriate.

4) People who want to own guns should be given the opportunity to demonstrate their ability to use them responsibly.

Points Which Gun Rights Advocates Should Concede:
1) Most gun control advocates are not raving lunatics, but ordinary citizens concerned about safety.

2) Some weapons are inappropriate for any legitimate purpose, and should be banned for private ownership.

3) It should be as easy as possible for police to connect a bullet at a crime scene to a particular gun, and trace the ownership of that gun. It should be as easy as finding the owner of a car given the license plate number.

4) Registering gun ownership is not necessarily the first step towards taking them all away.

And Now For the Asbestos Underwear
I happen to think that the eight points I listed above are completely obvious, and map out a fairly obvious middle ground. Nevertheless, for each of the points, I know people who would vehemently disagree with me (and consider my position to be proof that I'm a raving lunatic). Unfortunately, the institutions on both sides (lobbyists, public interest groups, etc.) are only motivated to polarize the debate.

If both sides will concede those eight points, however, the politics can move into more fruitful ground. The real debate should be over the parameters of allowable gun ownership and use:

1) What kinds of weapons are allowable and for what purposes, and what weapons can never be permitted for civilian ownership.

2) What is the most effective way to ensure that gun-related crimes can be solved as fast as possible for maximum deterrent effect (i.e. make prospective criminals think that "only an idiot uses a gun to commit a crime, because there's no way to get away with it").

3) What is the appropriate level of training and licensing for legal ownership of various types of weapons.

4) What is the most effective way to prevent gun-related accidents and suicides, especially among children.

5) How do we balance the concerns of those who are uncomfortable with guns against the desires of those who are willing and able to use them responsibly.