RCW 9.91.160
Personal protection spray devices.
(2) No town, city, county, special purpose district, quasi-municipal corporation or other unit of government may prohibit a person eighteen years old or older, or a person fourteen years old or older who has the permission of a parent or guardian to do so, from purchasing or possessing a personal protection spray device or from using such a device in a manner consistent with the authorized use of force under RCW 9A.16.020.