Let's have some cites on that revocation business.   Law enforcement can refer you to a mental health facility.   If it is determined that you pose a threat to yourself or others, the mental health facility may hold you; how long depends on the jurisdiction.   You have a right of habeas corpus to demand that a court make the determination.   If and only if a mental health professional makes a determination that you are a threat and you accept that determination or if you are adjudicated by a court to constitute a threat to yourself or others can your right to possess a firearm be suspended.   Mental health "professionals" in many states are very reluctant to make the necessary determination or if  the determination is made to notify proper authorities.   One of the primary weaknesses of the NICS database is state failure to properly report convictions and mental health adjudications, which allows otherwise ineligible people to acquire firearms.