A corollary that follows from the supremacy of federal law is that when a federal right, privilege or immunity is set up as a defense or authority for an act, opportunity shall exist for a final determination of this point in the federal courts. As has been earlier pointed out, the original Judiciary Act, passed in the first year of the Constitution, in its famous twenty-fifth section, provided that a final judgment or decree in any suit, in the highest court of law or equity of a State in which a decision of the suit could be had, "where is drawn in question the validity of a treaty or statute of, or an authority exercised under the United States, and the decision is against their validity, or where is drawn in question the validity of a statute of, or an authority exercised under any State, on the ground of their being repugnant to the Constitution, treaties or laws of the United States, and the decision is in favor of such their validity, or where is drawn in question the construction of any clause of the Constitution, or of a treaty, or statute of, or commission held under the United States, and the decision is against the title, right, privilege or exemption specially set up or claimed by either party, under such clause of the said Constitution, treaty, statute or commission may be re-examined and reversed or affirmed in the Supreme Court of the United States upon writ of error." In order that this appellate jurisdiction may be effectual this section also provides that instead of remanding the cause to the state court for a final decision therein, the Supreme Court may at their discretion, if the cause has been once before remanded, proceed to a final disposition of the same and award execution.

These provisions have remained substantially unchanged since their enactment to the present day.

It will be observed that provision for writ of error from the federal Supreme Court is made only for those eases in which the judgment in the state tribunals is adverse to the alleged federal right, privilege or immunity. Where the state decision is favorable there is, of course, no need, based upon the principle of federal supremacy, for a federal review.