The answer is, it doesn't say that. So basically, we just make stuff up as we go along in this country while along the way discriminating against the mentally ill. We interpret "the constitution" the way we want to interpret it, without any logical basis and wonder why we can't agree on anything. If the laws in this country have no logical basis they become a source of argument and confusion. And let's not confuse logic with common sense. Common sense is not the same as consistent logic. How 'bout we change "mentally ill" to "black", or "hispanic", or maybe "female" and see what it sounds like????The only way to treat EVERY individual in this country equal is to either let everyone bear arms or not let everyone bear arms otherwise we are guilty of discrimination and that is not what this country stands for.