D.C. Mun. Regs. tit. 17, r. 17-3319
A respondent may be represented only by an attorney who is an active member of the District of Columbia Bar, except that a board may permit an attorney who is an active member of the bar of another jurisdiction in the United States to represent a respondent in a particular case.
If it appears to a board or an Administrative Law Judge (ALJ) that the issues or facts in a matter before it are so complex that the interests of justice, saving time or facilitating the preparation of an adequate record would be served by the representation of a party by an attorney, the board may urge, but not require, that the party obtain the services of an attorney and may allow that party a reasonable period of time within which to do so.
An attorney shall not participate in a representative capacity in any hearing conducted by a board or ALJ until the attorney submits to a board or ALJ a signed statement containing the attorney's name, street address, telephone number, and bar number.
An attorney authorized to appear pursuant to this section may sign any paper required or permitted to be filed by this chapter.
D.C. Mun. Regs. tit. 17, r. 17-3319