American Bar Association Model Rules of Professional Conduct - Rule 1.12. Former Judge, Arbitrator, Mediator or Other Third-Party Neutral
(a) Except as stated in paragraph (d), a lawyer shall not represent anyone in connection with a matter in which the lawyer participated personally and substantially as a judge or other adjudicative officer or law clerk to such a person or as an arbitrator, mediator or other third-party neutral, unless all parties to the proceeding give informed consent, confirmed in writing.
(b) A lawyer shall not negotiate for employment with any person who is involved as a party or as lawyer for a party in a matter in which the lawyer is participating personally and substantially as a judge or other adjudicative officer or as an arbitrator, mediator or other third-party neutral. A lawyer serving as a law clerk to a judge or other adjudicative officer may negotiate for employment with a party or lawyer involved in a matter in which the clerk is participating personally and substantially, but only after the lawyer has notified the judge or other adjudicative officer.
(c) If a lawyer is disqualified by paragraph (a), no lawyer in a firm with which that lawyer is associated may knowingly undertake or continue representation in the matter unless:
(1) the disqualified lawyer is timely screened from any participation in the matter and is apportioned no part of the fee therefrom; and
(2) written notice is promptly given to the parties and any appropriate tribunal to enable them to ascertain compliance with the provisions of this rule.
(d) An arbitrator selected as a partisan of a party in a multimember arbitration panel is not prohibited from subsequently representing that party.