There is a general sales tax. Newspapers are specifically exempted, as is Food.
http://dor.wa.gov/Content/FindTaxesA...spx#interstate
And here
http://apps.leg.wa.gov/rcw/default.aspx?cite=82.08.0254 says The tax levied by RCW 82.08.020 shall not apply to sales which the state is prohibited from taxing under the Constitution of this state or the Constitution or laws of the United States.