All mentally ill? Seeking treatment for alcoholism or depression should bar firearm ownership? PTSD? For life? That's another issue Trump is far too vague on. Danger to self and others is a small subset of mental illnesses.
The people that used to be committed to mental institutions is what I am talking about, needs to be very well defined and subject to 2 or 3 party review.
PTSD, alcoholism, etc. are way different that that.
Even now, the VA seeks to disarm vets:
“The VA, in making the determination that a veteran requires a fiduciary to help them manage their money, is additionally making the decision that the veteran therefore cannot handle a firearm.”