ORS 34.040: When allowed.

(1) The writ shall be allowed in all cases in which a substantial interest of a plaintiff has been injured and an inferior court including an officer or tribunal other than an agency as defined in ORS 183.310 (1) in the exercise of judicial or quasi-judicial functions appears to have:

      (a) Exceeded its jurisdiction;

      (b) Failed to follow the procedure applicable to the matter before it;

      (c) Made a finding or order not supported by substantial evidence in the whole record;

      (d) Improperly construed the applicable law; or

      (e) Rendered a decision that is unconstitutional.

      (2) The fact that the right of appeal exists is no bar to the issuance of the writ.