courts) no further doubt can arise; for as
soon as it is established that a suit is Federal--that is to say, that
it belongs to the share of sovereignty reserved by the Constitution of
the Union--the natural consequence is that it should come within the
jurisdiction of a Federal court.

[Footnote h: This principle was in some measure restricted by the
introduction of the several States as independent powers into the
Senate, and by allowing them to vote separately in the House of
Representatives when the President is elected by that body. But these
are exceptions, and the contrary principle is the rule.]

Whenever the laws of the United States are attacked, or whenever they
are resorted to in self-defence, the Federal courts must be appealed to.
Thus the jurisdiction of the tribunals of the Union extends and narrows
its limits exactly in the same ratio as the sovereignty of the Union
augments or decreases. We have shown that the principal aim of the
legislators of 1789 was to divide the sovereign authority into two
parts. In the one they placed the control of all the general interests
of the Union, in the other the control of the special interests of
its component States. Their chief solicitude was to arm the Federal
Government with sufficient power to enable it to resist, within
its sphere, the encroachments of the several States. As for these
communities, the principle of independence within certain limits of
their own was adopted in their behalf; and they were concealed from the
inspection, and protected from the control, of the central Government.
In speaking of the division of authority, I observed that this latter
principle had not always been held sacred, since the States are
prevented from passing certain laws which apparently belong to their own
particular sphere of interest. When a State of the Union passes a law of
this kind, the citizens who are injured by its execution can appeal to
the Federal courts.

Thus the jurisdiction of the Federal courts extends not only to all the
cases which arise under the laws of the Union, but also to those
which arise under laws made by the several States in opposition to the
Constitution. The States are prohibited from making ex post facto laws
in criminal cases, and any person condemned by virtue of a law of this
kind can appeal to the judicial power of the Union. The States are
likewise prohibited from making laws which may have a tendency to impair
the obligations of c