16 C.F.R. § 1025.54
The Commission may, by order, review a case not otherwise appealed by a party. Should the Commission so order, the parties shall, and participants may, file briefs in accordance with § 1025.53 , except that the Commission may, in its discretion, establish a different briefing schedule in its order. The Commission shall issue its order within forty (40) days after issuance of the Initial Decision. The order shall set forth the issues which the Commission will review and may make provision for the filing of briefs. If the filing of briefs is scheduled by the Commission, the order shall designate which party or parties shall file the initial brief and which party or parties may thereafter file an answering brief, or the order may designate the simultaneous filing of briefs by the parties.
16 C.F.R. §1025.54