How do you reverse a mental incompetence ruling?

I'd like to know too. A recent celebrity case reminded me of this issue and it is

disturbing to me that it is possible for a judge to just unperson someone. Nobody worries about it much because it isn't abused much, and people really do have to turn to it often as loved one's grow senile or whatever. Also, if someone gets themselves out of a crime with an insanity defense or whatever, they asked for it. But still it is chilling that it is practiced at all. There should be another way, something in line with the rest of our whole system, which is predicated on assuming that people are responsible for themselves, ie have rights and responsibilities. Yeah, so how do you undo it?