Cal. Gov. Code § 31553

Elective officers become members of the retirement association on the first day of the calendar month following the filing of a declaration with the board to become a member, provided, however, that any such elective officer may, within 60 days after the expiration of the officer’s term of office or within 60 days after the officer ceases to hold the office, rescind the declaration and withdraw from the retirement association. In such cases, all contributions paid by the member shall be refunded in the same manner as applicable to members terminating service.