Wash. Rev. Code § 16.10.020
County commissioners may, if the situation so requires, establish dog control zones within high-density population districts, or other specified areas, of a county outside the corporate limits of any city, and outside the corporate limits of any organized township. For such zones, licensing regulations may be established which shall not necessarily be operative in sparsely settled rural districts, or in other portions of the county where they may not be needed. In determining the need for such zones, and in drawing their boundaries, county commissioners shall take into consideration the following factors:
[ 1969 c 72 s 2.]