Washington Revised Code Title 59. Landlord and Tenant § 59.12.060. Parties defendant

No person other than the tenant of the premises, and subtenant, if there be one, in the actual occupation of the premises when the complaint is filed, need be made parties defendant in any proceeding under this chapter, nor shall any proceeding abate, nor the plaintiff be nonsuited, for the nonjoinder of any person who might have been made party defendant; but when it appears that any of the parties served with process, or appearing in the proceeding, are guilty of the offense charged, judgment must be rendered against him or her. In case a person has become a subtenant of the premises in controversy after the service of any notice in this chapter provided for, the fact that such notice was not served on such subtenant shall constitute no defense to the action. All persons who enter the premises under the tenant, after the commencement of the action hereunder, shall be bound by the judgment the same as if they had been made parties to the action.