37 CFR § 2.19 - Revocation or withdrawal of attorney.
(1) Authority to represent an applicant, registrant or party to a proceeding before the Office may be revoked at any stage in the proceedings of a trademark case, upon written notification signed by the applicant, registrant, or party to the proceeding, or by someone with legal authority to bind the applicant, registrant, or party (e.g., a corporate officer or general partner of a partnership). In the case of joint applicants or joint registrants, all must sign.
(2) When a power of attorney is revoked, the Office will communicate directly with the applicant, registrant, or party to the proceeding, or with the new attorney or domestic representative if appropriate.
(3) A request to change the correspondence address does not revoke a power of attorney.
(4) A new power of attorney that meets the requirements of § 2.17(c) will be treated as a revocation of the previous power.
(b) Withdrawal of attorney. If the requirements of § 11.116 of this chapter are met, a practitioner authorized to represent an applicant, registrant, or party to a proceeding in a trademark case may withdraw upon application to and approval by the Director or, when applicable, upon motion granted by the Trademark Trial and Appeal Board. The practitioner should file the request to withdraw soon after the practitioner notifies the client of his/her intent to withdraw. The request must include the following:
(1) The application serial number, registration number, or proceeding number;
(2) A statement of the reason(s) for the request to withdraw; and
(i) A statement that the practitioner has given notice to the client that the practitioner is withdrawing from employment and will be filing the necessary documents with the Office; that the client was given notice of the withdrawal at least two months before the expiration of the response period, if applicable; that the practitioner has delivered to the client all documents and property in the practitioner's file concerning the application, registration or proceeding to which the client is entitled; and that the practitioner has notified the client of any responses that may be due, and of the deadline for response; or
(ii) If more than one qualified practitioner is of record, a statement that representation by co-counsel is ongoing.