The Army, or a local militia, can set the terms of applicants as they see fit.
I would not be in favor of lowering application standards, but of course the State cannot keep us safe, regardless of how high their entry standards (multiple articles have been written regarding physical fitness standards being lowered due to increasing childhood obesity and a PC desire to accept females in combat positions).
That said, please, let's recognize that those who set the terms of the debate often win the debate. "Mental Illness" is a synonym or euphemism for "Feeblemindedness", a term used by open Eugenicists in decades past. Open Eugenics being entirely repugnant, there is a requirement to shroud the language in deceptive and dangerous sounding terms.
While I wouldn't like to see people with histories of self-mutilation, depression / bi-polar disorder or substance abuse anywhere near firearms...I recognize that our Rights originate not with our mental fitness, sobriety or any other medically defined state of being, but that we are living humans! Let people be free and reap the whirlwind if they act improperly! Self-government, right?
“Men are qualified for civil liberty in exact proportion to their disposition to put moral chains on their own appetites—in proportion as their love to justice is above their rapacity;—in proportion as their soundness and sobriety of understanding is above their vanity and presumption;—in proportion as they are more disposed to listen to the counsels of the wise and good, in preference to the flattery of knaves. Society cannot exist unless a controlling power upon will and appetite be placed somewhere, and the less of it there is within, the more there is without. It is ordained in the eternal constitution of things that men of intemperate minds cannot be free. Their passions forge their fetters.” (Edmund Burke
, A Letter From Mr. Burke To A Member Of The National Assembly, 1791.)
But should the people of America once become capable of that deep simulation towards one another
, and towards foreign nations, which assumes the language of justice and moderation while it is practising iniquity and extravagance
, and displays I have received from Major-General Hull and Brigadier, General Walker your unanimous address from Lexington, animated with a martial spirit, and expressed with a military dignity becoming your character and the memorable plains on which it was adopted. in the most captivating manner the charming pictures of candor, frankness, and sincerity, while it is rioting in rapine and insolence, this country will be the most miserable habitation in the Nvorld; because we have no government armed with power capable of contending with human passions unbridled by morality and religion. Avarice, ambition, revenge, or gallantry, • would break the strongest cords of our Constitution as a whale goes through a net. Our Constitution was made only for a moral and religious people. It is wholly inadequate to the government of any other. -Message from John Adams
to the Officers of the First Brigade of the Third Division of the Militia of Massacusetts
October 11, 1798
What will govern men, an all powerful and all knowing State, or a deep and abiding national conscience, rooted in timeless precepts?
“A free people claim their rights, as derived from the laws of nature, and not as the gift of their chief magistrate.”
-Thomas Jefferson, 1774
Tweed Ring: "...we should have all done more to elected Republicans..." Agreed