If you have ANY history of mental illness you no getta a gun. Easier to eliminate that common denominator than all guns.
Difficult to regulate. When I worked for mental health, we had a client who had severe paranoid schizophrenia, who checked "No" on the mental illness question of the gun application and bought an assault rifle. We found out about it when he tried to buy the ammo (at Roses)...did not have enough money so laid it away. The Roses employee had concerns about him so called our emergency line. His illness was not stabilized. He believed he was in Vietnam and that the Vietnamese were trying to kill him and that he had t defend himself. (He had never been in the military) He lived in a neighborhood with lots of children. You can imagine what we feared. I finally convinced local law enforcement that this was a potentially dangerous situation and they called the ATF who called me. Those guys were awesome. They came up from Charlotte within hours and took him in custody. He went to a federal psychiatric facility. That Roses employee at the lay away desk may very well have saved several lives.
Don't understand why assault rifles, or semi automatic weapons are legal to buy. I think it is time that we outlawed weapons of mass destruction in the US.