California Code, Elections Code - ELEC § 2211

(a) Any person who (1) has plead not guilty by reason of insanity and who has been found to be not guilty pursuant to Section 1026 of the Penal Code, (2) has been found incompetent to stand trial and whose trial or judgment has been suspended pursuant to Section 1370 of the Penal Code, (3) has been convicted of a felony and who was judicially determined to be a mentally disordered sex offender pursuant to former Section 6300 of the Welfare and Institutions Code, as repealed by Chapter 928 of the Statutes of 1981, or (4) has been convicted of a felony and is being treated at a state hospital pursuant to Section 2684 of the Penal Code shall be disqualified from voting or registering to vote during that time that the person is involuntarily confined, pursuant to a court order, in a public or private facility.

(b) Upon the order of commitment to a treatment facility referred to in subdivision (a), the court shall notify the Secretary of State and the county elections official of the person's county of residence in the format prescribed by the Secretary of State and order the person to be disqualified from voting or registering to vote.

(c) If the person is later released from the public or private treatment facility, the court shall notify the Secretary of State and the county elections official of the person's county of residence in the format prescribed by the Secretary of State that the right of the person to register to vote is restored.

(d) This section shall remain in effect only until January 1, 2024, and as of that date is repealed.