Wash. Rev. Code § 10.89.010
Any member of a duly organized state, county or municipal peace unit of another state of the United States who enters this state in fresh pursuit, and continues within this state in such fresh pursuit, of a person in order to arrest the person on the ground that he or she is believed to have committed a felony in such other state or a violation of the laws of such other state relating to driving while intoxicated, driving under the influence of drugs or alcohol, driving while impaired, or reckless driving shall have the same authority to arrest and hold such person in custody as has any member of any duly organized state, county or municipal peace unit of this state, to arrest and hold in custody a person on the ground that he or she is believed to have committed a felony or a violation of the laws of such other state relating to driving while intoxicated, driving under the influence of drugs or alcohol, driving while impaired, or reckless driving in this state.
RCW 10.89.010