"And indeed, gentlemen, there exists a law, not written down anywhere but inborn in our hearts; a law which comes to us not by training or custom or reading but by derivation and absorption and adoption from nature itself; a law which has come to us not from theory but from practice, not by instruction but by natural intuition. I refer to the law which lays it down that, if our lives are endangered by plots or violence or armed robberies or enemies, any and every method of protecting ourselves is morally right. When weapons reduce them to silence, the laws no longer expect one to await their pronouncments. For people who decide to wait for these will have to wait for justice, too -- and meanwhile they suffer injustice first. Indeed, even the wisdom of the law itself, by a sort of tacit implication, permits self-defense, because it does not actually forbid men to kill; what it does, instead, is to forbid the bearing of a weapon with the intention to kill. When, therefore, an inquiry passes beyond the mere question of the weapon and starts to consider the motive, a man who has used arms in self-defense is not regarded as having carried them with a homicidal aim."
quoted on page 17 in Stephen P. Halbrook -- That Every Man Be Armed: The Evolution of a Constitutional Right . published in 1984, by The University of New Mexico Press and The Independent Institute.