RCW 59.18.400: Forcible entry or detainer or unlawful detainer actions—Writ of restitution—Answer of defendant.

On or before the day fixed for his appearance the defendant may appear and answer. The defendant in his answer may assert any legal or equitable defense or set-off arising out of the tenancy. If the complaint alleges that the tenancy should be terminated because the defendant tenant, subtenant, sublessee, or resident engaged in drug-related activity, or allowed any other person to engage in drug-related activity at the rental premises with his or her knowledge or consent, no set-off shall be allowed as a defense to the complaint.