10 CFR § 2.315 - Participation by a person not a party.
(a) A person who is not a party (including persons who are affiliated with or represented by a party) may, in the discretion of the presiding officer, be permitted to make a limited appearance by making an oral or written statement of his or her position on the issues at any session of the hearing or any prehearing conference within the limits and on the conditions fixed by the presiding officer. However, that person may not otherwise participate in the proceeding. Such statements of position shall not be considered evidence in the proceeding.
(b) The Secretary will give notice of a hearing to any person who requests it before the issuance of the notice of hearing, and will furnish a copy of the notice of hearing to any person who requests it thereafter. If a communication bears more than one signature, the Commission will give the notice to the person first signing unless the communication clearly indicates otherwise.
(c) The presiding officer will afford an interested State, local governmental body (county, municipality or other subdivision), and Federally-recognized Indian Tribe that has not been admitted as a party under § 2.309, a reasonable opportunity to participate in a hearing. The participation of any State, local governmental body, or Federally-recognized Indian Tribe shall be limited to unresolved issues and contentions, and issues and contentions that are raised after the State, local governmental body, or Federally-recognized Indian Tribe becomes a participant. Each State, local governmental body, and Federally-recognized Indian Tribe shall, in its request to participate in a hearing, designate a single representative for the hearing. The representative shall be permitted to introduce evidence, interrogate witnesses where cross examination by the parties is permitted, advise the Commission without requiring the representative to take a position with respect to the issue, file proposed findings in those proceedings where findings are permitted, and petition for review by the Commission under § 2.341 with respect to the admitted contentions. The representative shall identify those contentions on which they will participate in advance of any hearing held.
(d) If a matter is taken up by the Commission under § 2.341 or sua sponte, a person who is not a party may, in the discretion of the Commission, be permitted to file a brief “amicus curiae.” Such a person shall submit the amicus brief together with a motion for leave to do so which identifies the interest of the person and states the reasons why a brief is desirable. Unless the Commission provides otherwise, the brief must be filed within the time allowed to the party whose position the brief will support. A motion of a person who is not a party to participate in oral argument before the Commission will be granted at the discretion of the Commission.