Colo. R. App. P. 44.1 (2026)

(a) Challenge to Public Utilities Law or Act of Public Utilities Commission. If a party questions the validity, interpretation, or application of any section of the Public

Utilities Law of the State of Colorado or of any rule, regulation, order, certificate, or permit issued by the Public Utilities Commission in a proceeding in which the Commission is not a party, the questioning party must notify the clerk of the appellate court in writing immediately upon the filing of the proceeding or as soon as the question is raised in the appellate court. The clerk must then certify that fact to the Secretary of the Public Utilities Commission.

(b) Other Proceedings Impacting the Public Utilities Commission. In an appellate proceeding involving a municipally owned utility in which the court’s decision may impact the powers and duties of the Public Utilities Commission or the interpretation of the Public Utilities Law of the State of Colorado, the clerk of the appellate court must notify the Secretary of the Public Utilities Commission of the pendency of the proceeding and invite the Commission to intervene or to enter an appearance as amicus curiae.

Source: Rule and comment adopted and effective June 9, 2016.