(a) When applicable. A necessary party is a person or entity whose absence would prevent the Board from according complete relief among existing parties, or who claims an interest related to the subject of the proceeding such that reaching a determination in the proceeding may impair or impede that person's or entity's ability to protect that interest as a practical matter, or in whose absence an existing party would be subject to a substantial risk of incurring double, multiple, or inconsistent obligations because of that interest.

(b) Failure to join a necessary party. At any time, any party who believes in good faith that a necessary party has not been joined, and therefore the case is unsuitable for Board proceedings, may file a request according to the procedures set forth in §§ 220.5(a)(2) and 224.2(c) of this subchapter. Any party opposing the request may file a response according to the procedures set forth in §§ 220.5(a)(2) and 224.2(c). If the Board determines that a necessary party has not been joined, it shall dismiss the proceeding without prejudice as unsuitable for CCB proceedings pursuant to § 224.2.

(c) Intervention of a necessary party. At any time, a third party seeking to intervene on the ground(s) that it is a necessary party may file a request setting forth the reasons for the request and requesting a conference with the Board. Requests to intervene and any responses thereto shall follow the procedures set forth in § 220.5(a)(2) of this subchapter. After evaluating the parties' submissions, the Board may hold a conference between the parties to the proceeding and the intervening party to address the request.

(d) Board determination. (1) If the Board determines that the intervening party is not a necessary party, it shall deny the request and resume the proceeding, unless all parties agree that the party should be joined.

(2) If the Board determines that the intervening party is a necessary party, it shall—

(i) Permit the intervening party to join the proceeding, if no party indicated that it opposed the request to intervene; or

(ii) Dismiss the proceeding without prejudice, if any party indicated that it opposed the request to intervene.