Why do we bear arms? To effectively protect our lives and liberties, to enforce the Natural Law.
Why do State Fathers seek to disarm us? Paraphrasing Machiavelli, they distrust us either for cowardice or want of loyalty.
What is Lex Natura? Natural Law is that precept that states:
"The life and liberty of the individual must not be infringed upon."
As rational men, it is only just for Lex Natura to be enforced, for life and liberty to be safeguarded through whatever means necessary. This notion leads us to a problem:
"Which is the greater evil: spilling the blood of a man, or allowing him to spill the blood of ten?"
In both cases, Lex Natura is being infringed: in the former, by yourself; in the latter, by he whose flesh you stayed your blade from. When you think of it, the man who chose the former is far more merciful than he who chose the latter, for the blood of one man is on his hands in the first case, while the blood of ten men taint those hands in the second.
The desire of some State Fathers to disarm Lawful Juan is, in hindsight, foolish. Why? Simple: What they want is to paint a bull's-eye on Lawful Juan for Lawless Pedro and Oppressive Jose to shoot at with utter impunity, knowing that Juan no longer has a fighting chance against either. What they desire will only reinforce the culture of impunity that this society is notorious for. What they desire will only tighten the grip of Jose on Juan, until all that is left of the latter is a broken corpse--such is the usual fate of those victimized by totalitarianism.
How does Lex Natura fall into this? What these State Fathers seek is depriving law-abiding citizens of what is, frankly, one of the most efficient means of protecting their lives and liberties. It threatens Lex Natura. As disarming lawful citizens is an affront on the Natural Law, it can be considered unjust--and, per St. Augustine, the unjust law is no law.
If one were to say "Those who live by the sword shall die by the sword," it is only fitting to counter with "Those who bear no arms will always be at the mercy of those who do." Such is the harsh reality of the human state. Those who deny that fact will realize its veracity when they are in a situation in which there is nothing that can be done about it.