Well, this opens the door wide-open to all sorts of abuse, and must be watched with extreme care.
Don't forget that gun-banner's will consider you "mentally ill" for... you guessed it... wanting to own a gun.
That horse already left the wide-open barn door.
Those adjudicated mentally defective and anyone who has ever been committed to a mental institution are already in the prohibited persons category, and have been for years.
As imprecise as this wording is, it's just a result of laziness on the part of journalists.
If the gun banners want to block purchase by anyone suspected to be mentally ill, or who is prescribed antidepressants, or who wants to buy guns, they're going to have to try to change the law.
By the time I got down to your reply I saw that the tea leaves had already been read by yourself and others.
We have more laws than we need now!