37 CFR § 11.117 - Sale of law practice.
A practitioner or a law firm may sell or purchase a law practice, or an area of law practice, including good will, if the following conditions are satisfied:
(a) The seller ceases to engage in the private practice of law, or in the area of practice that has been sold, in a geographic area in which the practice has been conducted;
(1) Except as provided in paragraph (b)(2) of this section, the entire practice, or the entire area of practice, is sold to one or more lawyers or law firms;
(2) To the extent the practice or the area of practice involves patent proceedings before the Office, that practice or area of practice may be sold only to one or more registered practitioners or law firms that include at least one registered practitioner;
(1) The seller gives written notice to each of the seller's clients regarding:
(i) The proposed sale;
(ii) The client's right to retain other counsel or to take possession of the file; and
(iii) The fact that the client's consent to the transfer of the client's files will be presumed if the client does not take any action or does not otherwise object within ninety (90) days after receipt of the notice.
(2) If a client cannot be given notice, the representation of that client may be transferred to the purchaser only upon entry of an order so authorizing by a court having jurisdiction. The seller may disclose to the court in camera information relating to the representation only to the extent necessary to obtain an order authorizing the transfer of a file; and
(d) The fees charged clients shall not be increased by reason of the sale.