Wash. Rev. Code § 41.44.240
The right of a person to a pension, annuity or a retirement allowance, to the return of contribution, the pension, annuity or retirement allowance itself, any optional benefit, any other right accrued or accruing to any person under the provisions of this chapter, and the moneys in the fund created under this chapter shall not be subject to execution, garnishment, or any other process whatsoever whether the same be in actual possession of the person or be deposited or loaned. This section shall not apply to child support collection actions taken under chapter 26.18, 26.23, or 74.20A RCW against benefits payable under any such plan or arrangement. Benefits under this chapter shall be payable to a spouse or ex-spouse to the extent expressly provided for in any court decree of dissolution or legal separation or in any court order or court-approved property settlement agreement incident to any court decree of dissolution or legal separation.
RCW 41.44.240