[South40]

The individual states already decide who can and who cannot have a gun. http://www.ncsl.org/issues-research/justice/possession-of-a-firearm-by-the-mentally-ill.aspx

[arthurus]

The individual states already decide who can and who cannot have a gun.

UNCONSTITUTIONALLY!

"Shall not be infringed" is the operative wording here. There is no "except for" clause. When you stuff one into the Amendment you negate the Amendment entirely because you admit of the ability to interpret the Amendment to agree with your own trepidations.