of the first
importance, since its assertion of the final authority of the judicial
power, in the interpretation and enforcement of our written
constitutions, came to be accepted almost as an axiom of American
jurisprudence. In the course of his reasoning, Chief Justice Marshall
expressed in terms of unsurpassed clearness the principle which lay at
the root of his opinion. "It is," he declared, "emphatically the
province and duty of the judicial department to say what the law is....
If two laws conflict with each other, the courts must decide on the
operation of each.... If, then, the courts are to regard the
Constitution, and the Constitution is superior to any ordinary Act of
the Legislature, the Constitution and not such ordinary Act must govern
the case to which they both apply. Those, then, who controvert the
principle that the Constitution is to be considered in court as a
paramount law, are reduced to the necessity of maintaining that courts
must close their eyes on the Constitution and see only the law. This
doctrine would subvert the very foundation of all written
constitutions." In subsequently applying this rule, Marshall affirmed
that the courts ought never to declare an Act of Congress to be void
"unless upon a clear and strong conviction of its incompatibility with
the Constitution." Nevertheless, the power has been constantly and
frequently exercised; and there can be no doubt that from its exercise
the Supreme Court of the United States derives a political importance
not possessed by any other judicial tribunal.

While the supremacy of the Constitution was thus judicially asserted
over the acts of the national legislature, by another series of
decisions its proper supremacy over acts of the authorities of the
various States was in like manner vindicated. Of this series we may take
as an example Cohens _v_. Virginia, decided in 1828. In this case a
writ of error was obtained from the Supreme Court of the United States
to a court of the State of Virginia, in order to test the validity of a
statute of that State which was supposed to be in conflict with a law of
the United States. It was contended on the part of Virginia that the
Supreme Court could exercise no supervision over the decisions of the
State tribunals, and that the clause in the Judiciary Act of 1789 which
purported to confer such jurisdiction was invalid. In commenting upon
this argument, Chief Justice Marshall observed that if the Constituti