Good question. If it’s CA or CO, any geek on the street can denounce you to the po-po as a threat to others, and can do it anonymously. Rampant abuse guaranteed.
Originally, only a family member living under the same roof had standing to report you to police as a threat.
No psychiatric evaluation, no nothing; po-po goes to judge who issues warrant and your guns are gone and you spend the rest of your assets & life trying to prove you’re not crazy.
Orwell’s totalitarian nightmare is advancing on us, and quickly, along with the Thought Police.
Everything old is new again. How soon before we see the modern-day equivalents of these Venetian letter boxes where citizens could secretly post "rat'em-out" letters to the magistrate about their neighbors: 
They were called “Boche de leon” (lion's mouth), where the mouth was the letter drop.