David Hineline is right on the money.
I recently had an interesting conversation about the topic of being declared mentally incompetent. I was speaking with a county social worker who is assigned to the case of a friend of mine who is disabled with a neurological disorder that has severely limited her mobility and degraded her cognitive function to the point where she really can't manage her own affairs. I asked the social worker what it would take to have my friend declared incompetent and put under the care of a public administrator (her family is not able to care for her).
Her answer hit me like a lightning bolt:
Although my friend makes consistently bad decisions, is destroying the house her parents let her live in, relies on the charity of friends for food, and has run her finances into the ground she is still making her own decisions and is nowhere near legally incompetent.
We all make mistakes. People who have psychiatric disorders or decreased mental function have the same civil rights as the rest of us. At least here in the Occupied California Republic, getting someone declared legally incompetent is very, very difficult. It requires testimony of at least one psychiatrist and multiple witnesses.
I wouldn't leave a gun anywhere near my friend because I consider her a suicide risk, but she does have the right to buy one.