Wash. Rev. Code § 35.82.160
Any authority may submit to the attorney general of the state any bonds to be issued hereunder after all proceedings for the issuance of such bonds have been taken. Upon the submission of such proceedings to the attorney general, it shall be the duty of the attorney general to examine into and pass upon the validity of such bonds and the regularity of all proceedings in connection therewith. If such proceedings conform to the provisions of this chapter and are otherwise regular in form and if such bonds when delivered and paid for will constitute binding and legal obligations of the authority enforceable according to the terms thereof, the attorney general shall certify in substance upon the back of each of said bonds that it is issued in accordance with the Constitution and laws of the state of Washington.
RCW 35.82.160