Wash. Rev. Code § 53.18.030
In determining which employee organization will represent them, employees shall have maximum freedom in exercising their right of self-organization.
Controversies as to the choice of employee organization within a port shall be submitted to the public employment relations commission. Employee organizations may agree with the port district to independently resolve jurisdictional disputes: PROVIDED, That when no other procedure is available the procedures of RCW 49.08.010 shall be followed in resolving such disputes. In such case the chair of the public employment relations commission shall, at the request of any employee organization, arbitrate any dispute between employee organizations and enter a binding award in such dispute.
RCW 53.18.030
Powers and duties of public employment relations commission: Chapter 41.58 RCW.