Wash. Rev. Code § 81.04.450
Upon application of any person the commission shall furnish certified copies of any classification, rate, rule, regulation or order established by such commission, and the printed copies published by authority of the commission, or any certified copy of any such classification, rate, rule, regulation or order, with seal affixed, shall be admissible in evidence in any action or proceeding, and shall be sufficient to establish the fact that the charge, rate, rule, order or classification therein contained is the official act of the commission. When copies of any classification, rate, rule, regulation or order not contained in the printed reports, or copies of papers, accounts or records of public service companies filed with the commission shall be demanded from the commission for proper use, the commission shall charge a reasonable compensation therefor.
RCW 81.04.450