California Code, Code of Civil Procedure - CCP § 708.560

(a) Either the judgment creditor or the judgment debtor may apply to the court on noticed motion for an order to modify or set aside the assignment order. The notice of motion shall be served on the other party. Service shall be made personally or by mail.

(b) The court shall make an order modifying or setting aside the assignment order upon a showing that there has been a material change in circumstances since the time of the previous hearing on the assignment order. The court may order a reassignment of the right to payments as necessary. The order shall state whether and to what extent it applies to payments already made.