Cal. Gov. Code § 7508
A retired member of a state retirement system, other than the University of California Retirement System, the Judges' Retirement System, the Judges' Retirement System II, and the State Teachers' Retirement System, may, notwithstanding Section 9359.12, serve on a public board or commission and be entitled to receive for that service, per diem compensation for every day or portion thereof of actual attendance at meetings of the board or commission or any committee thereof, and necessary traveling expenses incurred in connection with the performance of his or her official duties, without loss or interruption of benefits provided by the system, so long as the service does not exceed a total of 50 meeting days.
This section shall not apply to service as a member of a board or commission the annual salary for which is prescribed by Chapter 6 (commencing with Section 11550) of Division 3 of Title 2.
Ca. Gov. Code § 7508