would have accomplished but half their work. No
definition can be so clear as to avoid the possibility of doubt; no
limitation so precise, as to exclude all uncertainty. Who, then, shall
construe this grant of the people? Who shall interpret their will, where
it may be supposed they have left it doubtful? With whom do they repose
this ultimate right of deciding on the powers of the government? Sir,
they have settled all this in the fullest manner. They have left it with
the government itself, in its appropriate branches. Sir, the very chief
end, the main design, for which the whole Constitution was framed and
adopted, was to establish a government that should not be obliged to act
through State agency, or depend on State opinion or State discretion.
The people had had quite enough of that kind of government under the
Confederation. Under that system, the legal action, the application of
law to individuals, belonged exclusively to the States. Congress could
only recommend; their acts were not of binding force, till the States
had adopted and sanctioned them. Are we in that condition still? Are we
yet at the mercy of State discretion and State construction? Sir, if we
are, then vain will be our attempt to maintain the Constitution under
which we sit.

But, sir, the people have wisely provided, in the Constitution itself, a
proper, suitable mode and tribunal for settling questions of
constitutional law. There are in the Constitution grants of powers to
Congress, and restrictions on these powers. There are also prohibitions
on the States. Some authority must, therefore, necessarily exist, having
the ultimate jurisdiction to fix and ascertain the interpretation of
these grants, restrictions, and prohibitions. The Constitution has
itself pointed out, ordained, and established that authority. How has it
accomplished this great and essential end? By declaring, sir, that "the
Constitution and the laws of the United States made in pursuance
thereof, shall be the supreme law of the land, any thing in the
Constitution or laws of any State to the contrary notwithstanding."

This, sir, was the first great step. By this the supremacy of the
Constitution and the laws of the United States is declared. The people
so will it. No State law is to be valid which comes in conflict with the
Constitution, or any law of the United States passed in pursuance of it.
But who shall decide this question of interference? To whom lies the
last appeal?