The term “party,” whenever used in this part, includes any natural person, corporation, association, firm, partnership, trustee, receiver, agency, public or private organization, government agency, or unit thereof representing said agency. A party who files a complaint under § 502.62 shall be designated as “complainant.” A party against whom relief or other affirmative action is sought in a proceeding commenced under § 502.62 or § 502.73 or a party named in an order of investigation issued by the Commission shall be designated as “respondent,” except that in investigations instituted under section 11(c) of the Shipping Act of 1984, 46 U.S.C. 41302(a)-(b), 41307(b), the parties to the agreement shall be designated as “proponents” and the parties protesting the agreement shall be designated as “protestants.” A person who has been permitted to intervene under § 502.68 shall be designated as “intervenor.” All parties and persons designated in this section shall be parties to the proceeding. No person other than a party or its representative may introduce evidence or examine witnesses at hearings. [Rule 41].

The Bureau of Enforcement shall be a party to proceedings upon designation by the Commission or upon leave to intervene granted pursuant to § 502.68. The Bureau's representative shall be served with copies of all papers, pleadings, and documents in every proceeding in which the Bureau is a party. The Bureau shall actively participate in any proceeding to which it is a party, to the extent required in the public interest, subject to the separation of functions required by section 5(c) of the Administrative Procedure Act. [Rule 42]

The Commission or presiding officer may order an appropriate substitution of parties in the event of a party's death, incompetence, transfer of its interest, or other appropriate circumstance. [Rule 43]