Cal. Gov't Code § 19140

(a) In addition to reinstatement required under any other section, an appointing power may, in his or her discretion, reinstate any person having probationary or permanent status who was separated from his or her position (1) by resignation, (2) by service retirement, (3) by termination from limited-term, temporary, career executive assignment, or exempt appointment, (4) under Section 19996.2, or (5) without a break in continuity of state service to accept another civil service or exempt appointment. In addition, an employee who was separated from his or her position under Section 19585 shall have permissive reinstatement eligibility to that position when he or she again meets the requirements for continuing employment in that position, and shall have permissive reinstatement eligibility for any other position as provided by this section.
(b) Reinstatement shall be undertaken subject to rule.
(c) Reinstatement shall be undertaken within three years if the employee, at the time of separation, was a member of the California Highway Patrol.
(d) For reinstatement after separation, for members of the California Highway Patrol, the time spent in any of the following positions shall not be considered in computing the three-year period:
1. (1) In a position which is exempt from civil service.
2. (2) As a temporary employee in another governmental agency engaged in a technical cooperation program under an agreement approved by the state.
3. (3) In a recognized military service.
(e) A member of the California Highway Patrol separated from state service may be reinstated to an otherwise appropriate nonmember class even if the separation exceeds three years.
(f) Reinstatement shall be made to any of the following vacant positions:
1. (1) The class vacated or from which separated.
2. (2) A lower class in the same series.
3. (3) Another class to which the employee could transfer or demote pursuant to rule.
  An employee, including a member of the California Highway Patrol, separated from his or her former position in state service by layoff, or by resignation or demotion in lieu of layoff, may be reinstated at the discretion of the appointing power. However, the reinstatement is subject to the requirements of this section and shall not be to a position that is specifically subject to the employee’s reemployment list eligibility.