37 CFR 11.109: Duties to former clients.

(a) A practitioner who has formerly represented a client in a matter shall not thereafter represent another person in the same or a substantially related matter in which that person's interests are materially adverse to the interests of the former client unless the former client gives informed consent, confirmed in writing.

(b) A practitioner shall not knowingly represent a person in the same or a substantially related matter in which a firm with which the practitioner formerly was associated had previously represented a client:

(1) Whose interests are materially adverse to that person; and

(2) About whom the practitioner had acquired information protected by §§ 11.106 and 11.109(c) that is material to the matter; unless the former client gives informed consent, confirmed in writing.

(c) A practitioner who has formerly represented a client in a matter or whose present or former firm has formerly represented a client in a matter shall not thereafter:

(1) Use information relating to the representation to the disadvantage of the former client except as the USPTO Rules of Professional Conduct would permit or require with respect to a client, or when the information has become generally known; or

(2) Reveal information relating to the representation except as the USPTO Rules of Professional Conduct would permit or require with respect to a client.