If we approach the question form the angle of what is a more affective way to prevent suicide, denying one method or early processional intervention and counseling then I think the latter wins hands down. Getting white males to report mode disorders is already extremely hard and attaching real world consequences that can effect not only their gun ownerships rights but potentially their employment prospects will only make things worse.
That doesn't mean I am against laws restricting ownership but if the bar is high enough to eliminate the threat of suppressing self reporting and don't think it will be effective except in a few fringe cases.