37 CFR § 11.108 - Conflict of interest; Current clients; Specific rules.
(a) A practitioner shall not enter into a business transaction with a client or knowingly acquire an ownership, possessory, security or other pecuniary interest adverse to a client unless:
(1) The transaction and terms on which the practitioner acquires the interest are fair and reasonable to the client and are fully disclosed and transmitted in writing in a manner that can be reasonably understood by the client;
(2) The client is advised in writing of the desirability of seeking and is given a reasonable opportunity to seek the advice of independent legal counsel in the transaction; and
(3) The client gives informed consent, in a writing signed by the client, to the essential terms of the transaction and the practitioner's role in the transaction, including whether the practitioner is representing the client in the transaction.
(b) A practitioner shall not use information relating to representation of a client to the disadvantage of the client unless the client gives informed consent, except as permitted or required by the USPTO Rules of Professional Conduct.
(c) A practitioner shall not solicit any substantial gift from a client, including a testamentary gift, or prepare on behalf of a client an instrument giving the practitioner or a person related to the practitioner any substantial gift unless the practitioner or other recipient of the gift is related to the client. For purposes of this paragraph, related persons include a spouse, child, grandchild, parent, grandparent or other relative or individual with whom the practitioner or the client maintains a close, familial relationship.
(d) Prior to the conclusion of representation of a client, a practitioner shall not make or negotiate an agreement giving the practitioner literary or media rights to a portrayal or account based in substantial part on information relating to the representation.
(1) A practitioner may advance court costs and expenses of litigation, the repayment of which may be contingent on the outcome of the matter;
(4) A practitioner may also advance any fee required to prevent or remedy an abandonment of a client's application by reason of an act or omission attributable to the practitioner and not to the client, whether or not the client is ultimately liable for such fee.
(f) A practitioner shall not accept compensation for representing a client from one other than the client unless:
(1) The client gives informed consent;
(2) There is no interference with the practitioner's independence of professional judgment or with the client-practitioner relationship; and
(3) Information relating to representation of a client is protected as required by § 11.106.
(g) A practitioner who represents two or more clients shall not participate in making an aggregate settlement of the claims of or against the clients, unless each client gives informed consent, in a writing signed by the client. The practitioner's disclosure shall include the existence and nature of all the claims involved and of the participation of each person in the settlement.
(h) A practitioner shall not:
(1) Make an agreement prospectively limiting the practitioner's liability to a client for malpractice unless the client is independently represented in making the agreement; or
(2) Settle a claim or potential claim for such liability with an unrepresented client or former client unless that person is advised in writing of the desirability of seeking and is given a reasonable opportunity to seek the advice of independent legal counsel in connection therewith.
(i) A practitioner shall not acquire a proprietary interest in the cause of action, subject matter of litigation, or a proceeding before the Office which the practitioner is conducting for a client, except that the practitioner may, subject to the other provisions in this section:
(1) Acquire a lien authorized by law to secure the practitioner's fee or expenses;
(2) Contract with a client for a reasonable contingent fee in a civil case; and
(3) In a patent case or a proceeding before the Office, take an interest in the patent or patent application as part or all of his or her fee.
(k) While practitioners are associated in a firm, a prohibition in paragraphs (a) through (i) of this section that applies to any one of them shall apply to all of them.