Cal. Gov. Code § 21198
A person who has been retired under this system for service following an involuntary termination of his or her employment, and who is subsequently reinstated to that employment pursuant to an administrative or judicial proceeding, shall be reinstated from retirement. The requirements of Section 21196 shall not apply to that reinstatement. Reinstatement shall be effective as of the date from which salary is awarded in the administrative or judicial proceedings, and his or her rights and obligations shall be as specified in this article. However, amounts paid to the person during retirement for any period after the date from which salary is awarded, shall be repaid by him or her to this system, and contributions shall be made for any period for which salary is awarded in the administrative or judicial proceedings in the amount that he or she would have contributed had his or her employment not been terminated, and he or she shall receive credit as state service for the period for which salary is awarded.
Ca. Gov. Code § 21198