If the right to bear arms was anything other than a consequence of the US Constitution -
which can be amended - then the other 95% of the world population would be claiming that right. But they are not, because it isn't. There is no such thing as a natural right; just rights granted by law.
The US Constitution is a piece of paper. It has been changed before; It can be changed again. It was written by human beings, and has been and will be amended by (or perhaps one day scrapped and replaced entirely by) human beings.
Human laws are not laws of nature.
I doubt 95 percent of the world's people are capable of agreeing on what natural rights are, or are not - the North Korean communist, Yemeni Muslim, and stick-hut dweller of Niger could not agree on the functions of indoor plumbing fixtures, let alone on the scope and meaning of natural rights.
Yet it is true that human laws are not natural laws, nor are they laws of ethics, morality, or philosophy. What they are, and on what basis they are made, is made by choice - be it the choice of a Stalin or by the parliament of Australia. But then, are we to assume, given your tone, that all "piece of paper" are the same, justified only because they are the will of the strongest and most powerful?
If not, then laws should also be based on something more, namely; a philosophical/moral view of the nature of men and what is right and wrong. One such view is that of natural rights and liberty - that of the individual as sovereign and entitled to free choice. And whether or not you agree, it remains true that the natural right to possess and use arms was not invented 'de novo' upon the creation of the Constitution.
I won't go into the history (although I am more than happy to provide citations for your reading) but many legal scholars have traced the beginnings of these rights in both ancient Chinese and Western philosophy, as well as Judaic and Islamic law . Invariably they derive from several other views of 'rights' and/or moral imperatives. In sum:
- The right of self-defense, and the use of weapons to harm or kill others.
- The right of a class, group, or citizenry to defend their interests against tyrants or oppressive classes.
- The duty to defend one's community or sovereign.
- The right to hunt or kill game, predators, and vermin.
Weapons are far more "natural" to human experience that are weapon bans. From the paleolithic to our own era the possession of weapons by both males and females has been ubiquitous and highly valued. So much so, skill in the martial arts has been a measure of every man's worth since antiquity - at one time, every proper "gentlemen" was expected to learn the sword or the bow or various other weapons (and to carry them in daily life).
Of course, there were ancients who opposed such rights - anyone defending the absolutist divine right of Kings or the Emperors "Heavenly Mandate" looked askance at such rights. Others, such as Muslims, saw nothing wrong with weapons as long as they weren't owned by the Jews and Christians within their empires. And some tyrants actually confiscated weapons from their common citizenry, fearful of rebellion or to secure a ruling class (e.g. the ban on sword ownership for non-Samurai peasants).
But deadly hand weapons are are more 'natural' (came before) than even the plow or the wheel. What could be more natural, more "human", than that?