Wash. Rev. Code § 53.40.120
The Reconstruction Finance Corporation, or any other agency of the United States government making any such loan, or any other holder or owner of any bonds issued pursuant to this chapter, shall not be required to see to the application of the moneys derived from such bonds to the purposes for which the bonds are issued as specified in any resolution authorizing the issuance thereof. No defense of invalidity, or irregularity in any such bonds funded or refunded by the issuance of bonds hereunder, shall be a valid defense in any action at law or equity for a judgment upon or for the enforcement or collection of any bonds issued pursuant to this chapter, and no court shall have jurisdiction to entertain any such defense in any such action or proceeding.
RCW 53.40.120