WAT §31602: (a) Each signature on a protest shall be acknowledged or proved in the manner required to entitle deeds to be recorded.

(a) Each signature on a protest shall be acknowledged or proved in the manner required to entitle deeds to be recorded. (b) A guardian, executor, administrator, or other person holding property in a trust capacity under appointment of court may sign a protest when authorized by the proper court, which authorization may be made without notice. A certified copy of such authorization shall be filed with such protest. (c) Where property is assessed in the name of a trustee or trustees, such trustee or trustees shall be deemed to be the person entitled to sign the protest. (d) The protest of any public or quasi-public corporation, private corporation, or unincorporated association may be signed by any person authorized by the board of directors or trustees or other managing body thereof, which authorization shall be in writing, attested by its seal, and duly acknowledged, and shall be filed with the board. (e) The owner of any property or interest therein, appearing upon the assessment role, which has been assessed in the wrong name or to unknown owners, or which has passed from the owner appearing as such on the last equalized assessment roll, since the same was made, shall be entitled to sign the protest represented thereby, either by the production of a proxy executed and acknowledged by such former owner, or by furnishing evidence of his ownership by a conveyance duly acknowledged showing the title to be vested in the person claiming the right to sign the protest, accompanied by a certificate of a competent searcher of titles, certifying that a search of the official records of the county since the date of the conveyance discloses no conveyance or transfer out from the grantee or transferee named in the conveyance. (f) Where the property has been contracted to be sold, the vendee shall be entitled to sign the protest, unless such real property is assessed in the name of the vendor, in which event the vendor shall be entitled to do so, unless the contract of sale otherwise expressly provides.