Did some quick research and it seems WA has adopted CA standards- both on emissions AND warranty coverage.

OP- you should not have an issue, although the SA might be a pita at first. Have your warranty book or other WA state document that shows the CA emissions should be followed.

They may insist on a charge to diagnose- either insist that they note "shall be $0 if any covered emissions defect" or jot that down on the work order when you sign it.