Cal. Government Code § 20301

Except as otherwise provided in this section, any person who on October 1, 1963, is employed by the university, and is a member of any retirement system maintained by the university, or who after that date enters university employment, shall be excluded from membership in this system. A university member who is separated from university employment due to layoff and who is reemployed by the university shall have the right to elect, in accordance with regulations of the board of regents, membership in this system in lieu of membership in any retirement system maintained by the university, if written notice of the election is filed with this system within 30 days after his or her reemployment. Any member who is employed as a member of the police department or fire department of the university and who elects, in accordance with regulations of the board of regents, to become a sworn officer member of a retirement system of the university in that employment shall be excluded from membership in this system in that employment after the date upon which he or she becomes a member of the university system. The election shall not constitute a permanent separation from state service for purposes of a right to refund of accumulated contributions, but shall constitute a discontinuance of employment as a member of this system and entry into employment as a member of the university system within the meaning of Section 20895.