Wash. Rev. Code § 49.36.015
No restraining order or injunction shall be granted by any court of this state, or any judge or judges thereof in any case between an employer and employee or between employer and employees or between employees or between persons employed and persons seeking employment involving or growing out of a dispute concerning terms or conditions of employment, unless necessary to prevent irreparable damage to property or to a personal right or to a property right of the party making the application, for which injury there is no adequate remedy at law, and such petition must be in writing describing such damage or injury feared by the applicant, and sworn to by the applicant or his or her agent or attorney. No such restraining order or injunction shall prohibit any such person or persons, whether singly or in concert, from terminating any relation of employment or from ceasing to perform any work or labor; or from paying or giving to, or withholding from any person engaged in such dispute, any strike benefits or other moneys or things of value; or from doing any act or thing which might lawfully be done in the absence of such dispute by any party thereto; nor shall any of the acts specified in this section be considered or held to be illegal or unlawful in any court of the state.
RCW 49.36.015
Labor disputes: Chapter 49.32 RCW.