RCW 41.59.910

This chapter shall supersede existing statutes not expressly repealed to the extent that there is a conflict between a provision of this chapter and those other statutes. Except as otherwise expressly provided herein, nothing in this chapter shall be construed to annul, modify or preclude the renewal or continuation of any lawful agreement entered into prior to January 1, 1976 between an employer and an employee organization covering wages, hours, and terms and conditions of employment. Where there is a conflict between any collective bargaining agreement and any resolution, rule, policy or regulation of the employer or its agents, the terms of the collective bargaining agreement shall prevail.