Wash. Rev. Code § 26.21A.405
(3) Except as provided in subsection (4) of this section and RCW 26.21A.410, the employer shall withhold and distribute the funds as directed in the withholding order by complying with terms of the order which specify:
(4) An employer shall comply with the law of the state of the obligor's principal place of employment for withholding from income with respect to:
[ 2002 c 198 s 502.]
Effective date—2002 c 198: See RCW 26.21A.900.