California Code, Family Code - FAM § 5270

(a) An obligor may move to quash an assignment order on any of the following grounds:

(b) If an assignment order is sought under Article 3 (commencing with Section 5250), the party ordered to pay support may also move to quash the service of the order based upon Section 5260.

(c) The obligor shall state under oath the ground on which the motion to quash is made.

(d) If an assignment order which has been issued and served on a prior employer is served on the obligor's new employer, the obligor does not have the right to move to quash the assignment order on any grounds which the obligor previously raised when the assignment order was served on the prior employer or on any grounds which the obligor could have raised when the assignment order was served on the prior employer but failed to raise.