D.C. Mun. Regs. tit. 1, § 1204
1204.1 In a proceeding before the Board, any person or party may:
(a) Appear on his or her own behalf; or
(b) Be represented by any other person duly authorized in writing to do so.
1204.2 An authorization provided pursuant to § 1204.1(b) shall be in a manner prescribed by the Board, and shall state either that the individual is an attorney duly licensed to practice law in the District or, if not an attorney duly licensed to practice law in the District of Columbia, that the authorization includes the power of the agent or representative to bind the person in the matter before the Board. An attorney licensed to practice law by a jurisdiction within the United States may represent a person before the Board.
SOURCE: Final Rulemaking published at 62 DCR 11123 (August 14, 2015).