"But, where the question is of a different nature, and capable of judicial inquiry and decision, there it admits of a very different consideration. The decision then made, whether in favor or against the constitutionality of the Act, by the State or by national authority, by the legislature or by the executive, being capable in its own nature of being brought to the test of the Constitution, is subject to judicial revision. It is in such cases, as we conceive, that there is a final and common arbiter provided by the Constitution itself, to whose decisions all others are subordinate; and that arbiter is the supreme judicial authority of the courts of the Union" (Story, Comm. Const. sec. 374, 375); for the Constitution declares, Art. 3, sec. 2, that "the judicial power shall extend to all cases in law and equity arising under this Constitution, the laws of the United States, and treaties made, or which shall be made, under their authority," &c. And Art. 3, sec. 1: "The judicial power of the United States shall be vested in one supreme court, and in such inferior courts as the Congress may from time to time ordain and establish."
These constitutional provisions are clear. The Constitution and laws and treaties of the United States are declared to be the supreme law of the land. To expound what the law is, is a judicial act. The judicial power extends to all cases arising under the Constitution, laws, and treaties of the United States. It therefore extends to the exposition of the Constitution, laws, and treaties, when the case before the court properly calls for such exposition. This judicial power, and consequently this power of exposition, it is declared, shall be vested in one supreme court, &c. Most obviously, the exposition given by this one supreme court cannot be overruled by any other constitutional power; else the court is not supreme, else the Constitution is nullified. The decision of the supreme court is the decision of the _only constitutionally authorized expounder of the meaning of the Constitution_; and such exposition, to be supreme, must be final.
What, then, has this final interpreter declared the meaning of these clauses of the Constitution to be?