Wash. Rev. Code § 47.32.120
Except as provided in RCW 47.04.270, it is unlawful for any person to erect a structure or establishment or maintain a business, the nature of which requires the use by patrons or customers of property adjoining the structure or establishment unless the structure or establishment is located at a distance from the right-of-way of any state highway so that none of the right-of-way thereof is required for the use of the patrons or customers of the establishment. Any such structure erected or business maintained that makes use of or tends to invite patrons to use the right-of-way or any portion thereof of any state highway by occupying it while a patron is a public nuisance, and the department may fence the right-of-way of the state highway to prevent such unauthorized use thereof.
RCW 47.32.120