Cal. Prob. Code § 4716

(a) If a patient lacks the capacity to make a health care decision, the patient’s domestic partner shall have the same authority as a spouse has to make a health care decision for his or her incapacitated spouse. This section may not be construed to expand or restrict the ability of a spouse to make a health care decision for an incapacitated spouse.
(b) For the purposes of this section, the following definitions shall apply:
1. (1) “Capacity” has the same meaning as defined in Section 4609.
2. (2) “Health care” has the same meaning as defined in Section 4615.
3. (3) “Health care decision” has the same meaning as defined in Section 4617.
4. (4) “Domestic partner” has the same meaning as that term is used in Section 297 of the Family Code.