28 U.S.C. § 2109 : US Code - Section 2109: Quorum of Supreme Court justices absent

      If a case brought to the Supreme Court by direct appeal from a
    district court cannot be heard and determined because of the
    absence of a quorum of qualified justices, the Chief Justice of the
    United States may order it remitted to the court of appeals for the
    circuit including the district in which the case arose, to be heard
    and determined by that court either sitting in banc or specially
    constituted and composed of the three circuit judges senior in
    commission who are able to sit, as such order may direct. The
    decision of such court shall be final and conclusive. In the event
    of the disqualification or disability of one or more of such
    circuit judges, such court shall be filled as provided in chapter
    15 of this title.
      In any other case brought to the Supreme Court for review, which
    cannot be heard and determined because of the absence of a quorum
    of qualified justices, if a majority of the qualified justices
    shall be of opinion that the case cannot be heard and determined at
    the next ensuing term, the court shall enter its order affirming
    the judgment of the court from which the case was brought for
    review with the same effect as upon affirmance by an equally
    divided court.