Cal. Gov. Code § 22152.7

Notwithstanding the provisions contained in a charter of any chartered city, the legislative body of such a city may by ordinance provide that employees may either add or combine old age, survivors, and disability insurance with any existing pension system. The board subsequent to the passage of such an ordinance may, pursuant to this part, divide the retirement system of such city for coverage of members of such system under the federal system upon terms and conditions as the board and legislative body may determine.