Cal. Government Code § 19996.37

(a) A permanent state employee or legislative employee who voluntarily reduces his or her worktime for partial service retirement pursuant to this article shall, upon request and subject to subdivision (b), be given priority for returning to a full-time work schedule to the extent that such full-time work is available; provided, that any employee who so voluntarily returns to full-time work shall be ineligible for five years thereafter to again participate pursuant to this article. The appointing authority may require a participating employee to return to full-time employment only if a state of emergency has been declared pursuant to Section 8558 which affects the area of the state in which the employee works. (b) A state employee or a legislative employee who is participating pursuant to this article in reduced worktime for partial service retirement may: (1) elect only once in each fiscal year to further reduce his or her worktime; (2) elect only once in five years to increase his or her worktime to another less than full-time schedule.