It is quite true that decisions of the Supreme Court are sometimes unpopular. People who are eager for humanitarian reforms, when they see the Supreme Court annulling measures which Congress has passed to protect women or children, or the weak or the poor, are in the habit of crying out that the court is an obstacle to progress and that its power to declare laws unconstitutional should be taken away. They overlook the fact that if there were no supreme tribunal to keep Congress within its constitutional limits, it would be easy for Congress, step by step, to take away all the powers now possessed by the states and to centralize at Washington the entire government of the country. Under a federal system of government, with powers divided between the nation and the states as they are in this country, disputes as to where a particular power belongs are sure to arise. How could we devise a more satisfactory plan of deciding these disputes than by referring them to an impartial body of nine men chosen for life from among the ablest jurists of the land? Do we propose to abolish the powers of juries because they sometimes render unpopular verdicts? People sometimes question the wisdom of the Supreme Court, but no one has ever doubted its integrity.[139] [Sidenote: Scope of the federal courts’ jurisdiction.] =How Cases Come Before the Federal Courts.=—The authority to try cases is divided by the national constitution into two parts, and each part is assigned to two separate systems of courts. Certain classes of cases are named in the national constitution as falling within “the judicial power of the United States” and these cases are tried in the federal courts. All other classes of cases (and this includes the great majority of legal disputes) are left to the state courts. The controversies named in the national constitution as matters for trial in the federal courts are those which it did not seem wise to let the various state courts decide, for example, cases arising out of treaties made by the United States, or controversies between two states, or between citizens of different states. This is a wise arrangement, for if the state courts could say the last word on the interpretation of treaties, the nation might easily find itself forced into trouble with foreign countries. If cases between citizens of different states were tried in the courts of either state, there would be a temptation for these courts to favor their own citizens. Even the rule which requires that cases affecting ambassadors shall be heard in the federal courts has a good reason, for the United States guarantees to all foreign ambassadors the privileges of international law and must be in a position to see that these guarantees are respected. The entire list of cases over which federal courts have jurisdiction is so clearly set forth in the constitution that there is no need for repeating it here.[140] [Sidenote: How jurisdiction is determined.]