Potter Stewart,
United States v. American-foreign Steamship Cor…
“ The reason for such a provision is not hard to discern. Congress would hardly have required a retired circuit judge to return to the bench to attend at an en banc hearing and, as between leaving the matter to the discretion of the individual judge and limiting the court to active judges, it is not surprising-in view of the varying degrees of judicial activity of the retired judges, and the administrative undesirability of having, for these purposes, a court of unpredictable size and complement-that Congress should have chosen the latter course. ”
