RCW 43.21A.430: Catalytic converters in police, ambulance or emergency aid vehicles—Department's powers restricted in respect thereto.

The department of ecology may not adopt, maintain in effect, or enforce any rule requiring the installation or maintenance of a catalytic converter in the exhaust system of any motor vehicle used as a police vehicle, or ambulance, an emergency aid vehicle, or a fire department vehicle, and any catalytic converter in the exhaust system of any such vehicle may be lawfully removed.