28 U.S.C. § 455 : US Code - Section 455: Disqualification of justice, judge, or magistrate judge

      (a) Any justice, judge, or magistrate judge of the United States
    shall disqualify himself in any proceeding in which his
    impartiality might reasonably be questioned.
      (b) He shall also disqualify himself in the following
    circumstances:
        (1) Where he has a personal bias or prejudice concerning a
      party, or personal knowledge of disputed evidentiary facts
      concerning the proceeding;
        (2) Where in private practice he served as lawyer in the matter
      in controversy, or a lawyer with whom he previously practiced law
      served during such association as a lawyer concerning the matter,
      or the judge or such lawyer has been a material witness
      concerning it;
        (3) Where he has served in governmental employment and in such
      capacity participated as counsel, adviser or material witness
      concerning the proceeding or expressed an opinion concerning the
      merits of the particular case in controversy;
        (4) He knows that he, individually or as a fiduciary, or his
      spouse or minor child residing in his household, has a financial
      interest in the subject matter in controversy or in a party to
      the proceeding, or any other interest that could be substantially
      affected by the outcome of the proceeding;
        (5) He or his spouse, or a person within the third degree of
      relationship to either of them, or the spouse of such a person:
          (i) Is a party to the proceeding, or an officer, director, or
        trustee of a party;
          (ii) Is acting as a lawyer in the proceeding;
          (iii) Is known by the judge to have an interest that could be
        substantially affected by the outcome of the proceeding;
          (iv) Is to the judge's knowledge likely to be a material
        witness in the proceeding.

      (c) A judge should inform himself about his personal and
    fiduciary financial interests, and make a reasonable effort to
    inform himself about the personal financial interests of his spouse
    and minor children residing in his household.
      (d) For the purposes of this section the following words or
    phrases shall have the meaning indicated:
        (1) "proceeding" includes pretrial, trial, appellate review, or
      other stages of litigation;
        (2) the degree of relationship is calculated according to the
      civil law system;
        (3) "fiduciary" includes such relationships as executor,
      administrator, trustee, and guardian;
        (4) "financial interest" means ownership of a legal or
      equitable interest, however small, or a relationship as director,
      adviser, or other active participant in the affairs of a party,
      except that:
          (i) Ownership in a mutual or common investment fund that
        holds securities is not a "financial interest" in such
        securities unless the judge participates in the management of
        the fund;
          (ii) An office in an educational, religious, charitable,
        fraternal, or civic organization is not a "financial interest"
        in securities held by the organization;
          (iii) The proprietary interest of a policyholder in a mutual
        insurance company, of a depositor in a mutual savings
        association, or a similar proprietary interest, is a "financial
        interest" in the organization only if the outcome of the
        proceeding could substantially affect the value of the
        interest;
          (iv) Ownership of government securities is a "financial
        interest" in the issuer only if the outcome of the proceeding
        could substantially affect the value of the securities.

      (e) No justice, judge, or magistrate judge shall accept from the
    parties to the proceeding a waiver of any ground for
    disqualification enumerated in subsection (b). Where the ground for
    disqualification arises only under subsection (a), waiver may be
    accepted provided it is preceded by a full disclosure on the record
    of the basis for disqualification.
      (f) Notwithstanding the preceding provisions of this section, if
    any justice, judge, magistrate judge, or bankruptcy judge to whom a
    matter has been assigned would be disqualified, after substantial
    judicial time has been devoted to the matter, because of the
    appearance or discovery, after the matter was assigned to him or
    her, that he or she individually or as a fiduciary, or his or her
    spouse or minor child residing in his or her household, has a
    financial interest in a party (other than an interest that could be
    substantially affected by the outcome), disqualification is not
    required if the justice, judge, magistrate judge, bankruptcy judge,
    spouse or minor child, as the case may be, divests himself or
    herself of the interest that provides the grounds for the
    disqualification.