There thus remains a measure of doubt that Con- gress’s power over the federal courts is as plenary as some of the Court’s language suggests it is. Congress has a vast amount of discretion in conferring and withdrawing and structuring the original and appellate jurisdiction of the inferior federal courts and the appellate jurisdiction of the Supreme Court; so much is clear from the practice since 1789 and the holdings of many Court decisions. That its power extends to accomplishing by means of its control over jurisdiction actions which it could not do directly by substantive enactment is by no means clear from the text of the Constitution or from the cases.