29 C.F.R. § 1603.303 – Briefs on appeal.

(a) The appellant shall file a brief or other written statement within 30 days after the appeal is filed, unless the Commission otherwise directs.
(b) All other parties may file briefs or other written statements within 30 days of service of the appellant's brief or statement.
(c) Every brief or statement shall contain a statement of facts and a section setting forth the party's legal arguments. Any brief or statement in support of the appeal shall contain arguments or evidence that tend to establish that the dismissal, order or decision:
1. (1) Is not supported by substantial evidence;
2. (2) Contains an erroneous interpretation of law, regulation or material fact, or misapplication of established policy;
3. (3) Contains a prejudicial error of procedure; or
4. (4) Involves a substantial question of law or policy.
(d) Appellate briefs shall not exceed 50 pages in length.
(e) Filing and service of the appeal and appellate briefs shall be made in accordance with § 1603.209.