Curtis in Taylor _v._ Morton:[192] It is not "a judicial
question, whether a treaty with a foreign sovereign has been violated by
him; whether the consideration of a particular stipulation in a treaty,
has been voluntarily withdrawn by one party, so that it is no longer
obligatory on the other; whether the views and acts of a foreign
sovereign, manifested through his representative have given just
occasion to the political departments of our government to withhold the
execution of a promise contained in a treaty, or to act in direct
contravention of such promise. * * * These powers have not been confided
by the people to the judiciary, which has no suitable means to exercise
them; but to the executive and the legislative departments of our
government. They belong to diplomacy and legislation, and not to the
administration of existing laws. And it necessarily follows, that if
they are denied to Congress and the Executive, in the exercise of their
legislative power, they can be found nowhere, in our system of
government." Chief Justice Marshall's language in Foster _v._
Neilson[193] is to the same effect.

TREATIES AND THE NECESSARY AND PROPER CLAUSE

What power, or powers, does Congress exercise when it enacts legislation
for the purpose of carrying treaties of the United States into effect?
When the subject matter of the treaty falls within the ambit of
Congress's enumerated powers (those listed in the first 17 clauses of
article I, section 8 of the Constitution), then it is these powers which
it exercises in carrying such treaty into effect. But if the treaty
deals with a subject which falls normally to the States to legislate
upon, or a subject which falls within the national jurisdiction because
of its international character, then recourse is had to the necessary
and proper clause. Thus, of itself, Congress would have no power to
confer judicial powers upon foreign consuls in the United States, but
the treaty-power can do this and has done it repeatedly and Congress has
supplemented these treaties by appropriate legislation.[194] Again,
Congress could not confer judicial power upon American consuls abroad to
be there exercised over American citizens, but the treaty-power can and
has, and Congress has passed legislation perfecting such agreements and
such legislation has been upheld.[195] Again, Congress of itself could
not provide for the extradition of fugitives from justice, but the
treaty-power can and has do