Restatement of the Law Governing Lawyers (ALI, 2000)
§ 122. Client Consent to a Conflict of Interest
(1) A lawyer may represent a client notwithstanding a conflict of interest prohibited by §121 if each affected client or former client gives informed consent to the lawyer’s representation. Informed consent requires that the client or former client have reasonably adequate information about the material risks of such representation to that client or former client.
(2) Notwithstanding the informed consent of each affected client or former client, a lawyer may not represent a client if:
(a) the representation is prohibited by law;
(b) one client will assert a claim against the other in the same litigation; or
(c) in the circumstances, it is not reasonably likely that the lawyer will be able to provide adequate representation to one or more of the clients.