ns these personages concerns in some
degree the whole Union. When an ambassador is a party in a suit, that
suit affects the welfare of the nation, and a Federal tribunal is
naturally called upon to decide it.

The Union itself may be invoked in legal proceedings, and in this case
it would be alike contrary to the customs of all nations and to common
sense to appeal to a tribunal representing any other sovereignty
than its own; the Federal courts, therefore, take cognizance of these
affairs.

When two parties belonging to two different States are engaged in a
suit, the case cannot with propriety be brought before a court of either
State. The surest expedient is to select a tribunal like that of the
Union, which can excite the suspicions of neither party, and which
offers the most natural as well as the most certain remedy.

When the two parties are not private individuals, but States, an
important political consideration is added to the same motive of equity.
The quality of the parties in this case gives a national importance to
all their disputes; and the most trifling litigation of the States may
be said to involve the peace of the whole Union. *f

[Footnote f: The Constitution also says that the Federal courts shall
decide "controversies between a State and the citizens of another
State." And here a most important question of a constitutional nature
arose, which was, whether the jurisdiction given by the Constitution in
cases in which a State is a party extended to suits brought against a
State as well as by it, or was exclusively confined to the latter. The
question was most elaborately considered in the case of Chisholm v.
Georgia, and was decided by the majority of the Supreme Court in the
affirmative. The decision created general alarm among the States, and
an amendment was proposed and ratified by which the power was entirely
taken away, so far as it regards suits brought against a State. See
Story's "Commentaries," p. 624, or in the large edition Section 1677.]

The nature of the cause frequently prescribes the rule of competency.
Thus all the questions which concern maritime commerce evidently fall
under the cognizance of the Federal tribunals. *g Almost all these
questions are connected with the interpretation of the law of nations,
and in this respect they essentially interest the Union in relation to
foreign powers. Moreover, as the sea is not included within the limits
of any peculiar jurisdiction, t