I take the view that some rights are logically antecedent to anything of a conventional nature such as a group decision or a constitution. Thus the right to life is not conferred by any constitution, but recognized and protected by well-crafted ones. In simple terms, you don't have the right to life because some people say you do; they correctly say you do because you have this right quite apart from anything they say. The right to life is a natural right. It is logically antecedent to anything of a conventional nature such as the positive law.
If there are some natural rights, then whether we have a right to life, or any natural right, cannot depend on the interpretation of any man-made document. Therefore, with respect to the question of gun rights, the interpretation of the Second Amendment to the Constitution of the United States, albeit important, is logically secondary. The logically prior question is whether there are natural gun rights that need constitutional codification, recognition, and protection.
Th notion that one has a natural right to own a gun may sound absurd, but if I can derive the right to own a gun from the natural right to life, then I will have gone some distance toward showing that the right to own a gun — or more generally, the right to procure for oneself the means of self-defense — is a natural right.
So here is my argument.
1. Every human person possesses a natural right to life.
2. If every human person has a natural right to life, then he has a right to defend his life against those who would seek to violate this right.
3. If every human person has a right to defend his life, then he has a right to an effective means of defending his life.
Therefore
4. Every human person has a right to an effective means of defending his life. (From 1, 2, 3 by Modus Ponens and Hypothetical Syllogism.)
5. In many circumstances, a gun is the only effective means of defending one's life.
Therefore
6. In many circumstances, human persons have a right to possess guns, a right that is not conferred by constitutions but ought to be respected by them.
The conclusions (4) and (6) follow from the premises, though I might need to think more about the logic of the move from (4) and (5) to (6). (What exactly is the form of the argument and the validating rules of inference?) But are the premises defensible? I maintain that they are.
I take (1) to be axiomatic. In any case it is here assumed and cannot be here defended. Note that the argument does not assume that every human being is a human person. Charles Manson is a human being, but it is arguable that by the commission of his crimes he forfeited his personhood, and with it his right to life. Some will hold that human fetuses are not persons, and so have no right to life. I believe they are wrong, but the above argument does not rest on the assumption that they are.
To see that (2) is true, consider what happens if you negate it. The negation of (2) is: (~2) Human persons have a right to life, but they do not have the right to defend their lives. The absurdity of this is self-evident. How could I have a right to life if it is morally impermissible for me to defend my life? My having a right to life may not entail any moral obligation on my part to defend my life, but it surely entails the moral permissibility of self-defense. For if I have a right to life, then others have an obligation not to harm me. This obligation of theirs entitles me to meet a deadly threat with force sufficient to thwart the attack up to and including killing the assailant. We appear to be at moral rock-bottom here. I say (2) is self-evident. Reject it, and there is probably no point in further discussion. It is meaningless to affirm a right to life while denying the right to defend one's life.
I don't know exactly how to explain what a right is, but it is something like an entitlement (is this a case of obscurum per obscurius?) If I have a right to X, then I am entitled to X, and that entitlement grounds the moral permissibility of my defending my pursuit of or possession of X. We are at rock bottom. My spade is turned as old Ludwig might have said.
We now turn to (3): If a human person has a right to defend his life, then he has a right to an effective means of defending his life. The negation of (3) also strikes me as absurd: You have a right to defend yourself, but no right to the possession of any effective means of so doing? In rebuttal of this absurdity consider the following.
To will the end is to will the means. So, to will one's defense is to will the means to one's defense. Therefore, if it is morally permissible to will one's defense, then it is morally permissible to will the means to one's defense. To will the means to one's defense is to will the possession of, and the ability to use, sufficient means for one's defense. I grant that qualifications may be needed. Arguably, felons ought not have the right to purchase firearms. A felon either forfeits his right to self-defense, or has that right overridden by the community's right to be safe from his predation. The right to own a weapon for self-defense, even if derivable from the natural right to life, is like the right to life itself: in some circumstances it is forfeited.
But how could the natural right to life be forfeited? How could one lose such a right? Suppose that you, unprovoked, attack me with deadly force with the intent to kill me. I am justified in killing you if that is what it takes to stop your deadly attack. If I am so justified, then my killing you is morally permissible. Now if your right to life was not forfeited by you at the moment you attempted to kill me, then your right to life would generate in me the correlative duty to respect your life by refraining from any and all actions that might harm it. It would then be impermissible for me to kill you. Therefore, if one who possess a right to life cannot ever, by anything he does, forfeit the right to life, then my killing you is both permissible and impermissible. But that is a contradiction. I conclude that there are circumstances in which a person forfeits his right to life.
So I don't see any problem with a person's possession of natural rights that can be forfeited by the person's free acts. There is also the case of capital punishment. 'Surely' capital punishiment is in some cases not only morally permissible, but morally obligatory: justice in some cases demands it. Well, if you agree with that, then you have to grant either that the natural right to life can be forfeited or else overridden.
(5) is obviously true pending some obvious qualifications that I left out for the sake of brevity, the soul of wit and of blog. A gun is an effective means of self defense, but not in all circumstances, only if the defender is properly trained in the use of firearms, etc.
The conclusion follows from the premises, and the premises are defensible. So I say the individual qua individual (as opposed to the individual qua member of some collective such as a police force or military unit) has an individual right to possess firearms for the purpose of defending his own life. The existence of such an individual right does not entail that it is unlimited. Thus if I have a right to firepower sufficient to my self-defense, it does not follow that I have a right to firepower sufficient to lay waste to a city. One non sequitur to avoid is this: There is no unlimited individual right to keep and bear arms; ergo, the right to keep and bear arms is a collective right.
Arguments like the foregoing make appeal to people's reason. Like all my arguments, the above argument is directed to open-minded, reasonable people who are doing their level best to form correct opinions about matters of moment. You decide whether I have been employing right reason. But if you wish to criticize, just be sure that you engage what I have actually written and not something you have excogitated on the occasion of skimming my post.