California Code, Government Code - GOV § 31542

(a) The board shall establish a procedure for assessing and determining whether an element of compensation was paid to enhance a member's retirement benefit. If the board determines that compensation was paid to enhance a member's benefit, the member or the employer may present evidence that the compensation was not paid for that purpose. Upon receipt of sufficient evidence to the contrary, a board may reverse its determination that compensation was paid to enhance a member's retirement benefits.

(b) Upon a final determination by the board that compensation was paid to enhance a member's retirement benefit, the board shall provide notice of that determination to the member and employer. The member or employer may obtain judicial review of the board's action by filing a petition for writ of mandate within 30 days of the mailing of that notice.

(c) Compensation that a member was entitled to receive pursuant to a collective bargaining agreement that was subsequently deferred or otherwise modified as a result of a negotiated amendment of that agreement shall be considered compensation earnable and shall not be deemed to have been paid to enhance a member's retirement benefit.