California Code, Education Code - EDC § 22508

(a) A member who becomes employed by the same or a different school district or community college district, or a county superintendent, or who becomes employed by the state in a position described in subdivision (b), to perform service that requires membership in a different public retirement system, and who is not excluded from membership in that public retirement system, may elect to have that service subject to coverage by the Defined Benefit Program of this plan and excluded from coverage by the other public retirement system. If that election is made, the service performed for the employer in that position as of the date of hire shall be considered creditable service for purposes of this part.

(b) Subdivision (a) shall apply to a member who becomes employed by the state only if the member is also one of the following:

(c) A member of the Public Employees' Retirement System who is subsequently employed to perform creditable service requiring coverage by the Defined Benefit Program of this plan may elect to have that subsequent service subject to coverage by the Public Employees' Retirement System and excluded from coverage by the Defined Benefit Program pursuant to Section 20309 of the Government Code.

(d) An election made by a member pursuant to this section shall be irrevocable.