American Bar Association Model Rules of Professional Conduct - Rule 2.4. Lawyer Serving as Third-Party Neutral
(a) A lawyer serves as a third-party neutral when the lawyer assists two or more persons who are not clients of the lawyer to reach a resolution of a dispute or other matter that has arisen between them. Service as a third-party neutral may include service as an arbitrator, a mediator or in such other capacity as will enable the lawyer to assist the parties to resolve the matter.
(b) A lawyer serving as a third-party neutral shall inform unrepresented parties that the lawyer is not representing them. When the lawyer knows or reasonably should know that a party does not understand the lawyer's role in the matter, the lawyer shall explain the difference between the lawyer's role as a third-party neutral and a lawyer's role as one who represents a client.