Define mental illness!
Is it someone who takes antidepressants?
Is it someone who is always depressed?
Is it someone who has Aspergers?
Is it someone who is Autistic?
What about those who have Downs Syndrome? Is that a mental illness?
Maybe only those who are diagnosed as psychotic.
Maybe it's someone who is only dangerously Autistic!
Maybe it's just that weird guy who lives alone at the end of your street!
How do we determine who is merely mentally ill and those who are dangerous? What do we do with those who are dangerous?
We need to have a place for these people to go when they need help and we need to give them help even when they cannot pay for it. Right now, in the US, there few places for people who have money to go when they need mental help, much less for people who do not have the means to pay for treatment. Insurance is no help. Have you looked at your health insurance? How much help will your policy give you if you need mental health treatment? What happens to your health insurance if you are unable to work?
A law that prevents people with mental illnesses from owning guns may be warranted, but with the proliferation of guns in our society, it's not difficult for them to get guns and ammo anyway. What we need is better identification of mental illness and widely available treatment opportunities for people with mental illnesses.