43 CFR §4.108

1. (a)Intervention—(1) Motion to intervene. Any person or entity that wants to participate in a proceeding as an intervenor must file a written motion and must serve a copy of the motion on all parties to the proceeding.
   1. (2)Who may request intervention. A person or entity may seek intervention if:
      1. (i)The person or entity had a legal right to initiate the proceeding; or
      2. (ii)The person or entity has an interest that could be adversely affected by the outcome of the proceeding.
   2. (3)Contents of motion. A motion to intervene must contain:
      1. (i)The factual and legal basis supporting the motion to intervene, including citations to any applicable legal authority; and
      2. (ii)A statement indicating when the person or entity requesting intervention learned of the proceeding.
   3. (4)Ruling on motion. The ALJ may:
      1. (i)Grant the motion;
      2. (ii)Grant the motion but limit participation by the person or entity; or
      3. (iii)Deny the motion if:
         1. (A)The movant fails to meet the requirements of this section; or
         2. (B)The ALJ determines that granting the motion would materially prejudice the existing parties or unduly delay adjudication of the proceeding.
   4. (5)Party status. A person or entity granted full or limited intervenor status is a party to the proceeding. If the ALJ denies the motion to intervene, the ALJ may allow the person or entity to file a brief as amicus curiae.
2. (b)Amicus curiae—(1) How to request amicus curiae status. Any person or entity that wants to file a brief in the proceeding as amicus curiae must file a written motion. The motion must describe the interest of the person or entity in the proceeding and explain how an amicus brief will contribute to the resolution of the issues. The motion must be served on all parties to the proceeding.
   1. (2)Ruling on motion. The ALJ has the discretion to grant or deny the motion and may consider any relevant factors, including whether an amicus brief would contribute to the resolution of the issues or cause undue delay.
   2. (3)Party status. A person or entity granted amicus curiae status is not a party to the proceeding.
   3. (4)Amicus brief. A person or entity granted amicus curiae status must serve its brief on all parties to the proceeding.