California Code, Family Code - FAM § 299.6

(a) Any local ordinance or law that provides for the creation of a “domestic partnership” shall be preempted on and after July 1, 2000, except as provided in subdivision (c).

(b) Domestic partnerships created under any local domestic partnership ordinance or law before July 1, 2000, shall remain valid. On and after July 1, 2000, domestic partnerships previously established under a local ordinance or law shall be governed by this division and the rights and duties of the partners shall be those set out in this division, except as provided in subdivision (c), provided a Declaration of Domestic Partnership is filed by the domestic partners under Section 298.5.

(c) Any local jurisdiction may retain or adopt ordinances, policies, or laws that offer rights within that jurisdiction to domestic partners as defined by Section 297 or as more broadly defined by the local jurisdiction's ordinances, policies, or laws, or that impose duties upon third parties regarding domestic partners as defined by Section 297 or as more broadly defined by the local jurisdiction's ordinances, policies, or laws, that are in addition to the rights and duties set out in this division, and the local rights may be conditioned upon the agreement of the domestic partners to assume the additional obligations set forth in this division.