It's only a matter to time, that governments will decides that 'Public safety' outweighs 'Privacy Concerns' and a Dr. will be required by law to flag you, if he feels you're mentally unstable, thereby making it impossible for you to ever get a firearm license or have the one you have taken away.
At present, volunteering of that information seems not to be working. In most of the aftermaths, they find the shooters were know to or suspected of being unstable, yet had legal firearms.