Wash. Rev. Code § 39.06.010
Contracts with unregistered or unlicensed contractors and with other violators prohibited
No agency of the state or any of its political subdivisions may execute a contract:(1) With any contractor who is not registered or licensed as may be required by the laws of this state other than contractors on highway projects who have been prequalified as required by RCW 47.28.070, with the department of transportat…