Cal. WIC § 6002

(a) The person in charge of a private institution, hospital, or clinic that is conducted for, or includes a department or unit conducted for, the care and treatment of persons who have mental health disorders may receive therein as a voluntary patient a person with a mental health disorder who is a suitable person for care and treatment in the institution, hospital, or clinic who voluntarily makes a written application to the person in charge for admission into the institution, hospital, or clinic and who is, at the time of making the application, mentally competent to make the application. A conservatee, with a conservator of the person, or person and estate, appointed under Chapter 3 (commencing with Section 5350) of Part 1 of Division 5, with the right as specified by court order under Section 5358 to place his conservatee, may be admitted upon written application by his or her conservator.

(b) After the admission of a voluntary patient to a private institution, hospital, or clinic, the person in charge shall forward to the office of the State Department of State Hospitals a record of the voluntary patient showing all information required by rule by the department.

(c) A voluntary adult patient may leave the hospital, clinic, or institution at any time by giving notice of his or her desire to leave to a member of the hospital staff and completing normal hospitalization departure procedures. A conservatee may leave in a like manner if notice is given by his or her conservator.