37 CFR §11.112

1. (a)Except as stated in paragraph (d) of this section, a practitioner shall not represent anyone in connection with a matter in which the practitioner 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.
2. (b)A practitioner shall not negotiate for employment with any person who is involved as a party or as practitioner for a party in a matter in which the practitioner is participating personally and substantially as a judge or other adjudicative officer or as an arbitrator, mediator or other third-party neutral. A practitioner serving as a law clerk to a judge or other adjudicative officer may negotiate for employment with a party or practitioner involved in a matter in which the clerk is participating personally and substantially, but only after the practitioner has notified the judge, or other adjudicative officer.
3. (c)If a practitioner is disqualified by paragraph (a) of this section, no practitioner in a firm with which that practitioner is associated may knowingly undertake or continue representation in the matter unless:
   1. (1)The disqualified practitioner is timely screened from any participation in the matter and is apportioned no part of the fee therefrom; and
   2. (2)Written notice is promptly given to the parties and any appropriate tribunal to enable them to ascertain compliance with the provisions of this section.
4. (d)An arbitrator selected as a partisan of a party in a multimember arbitration panel is not prohibited from subsequently representing that party.