The federal power has also been extended at the expense of the states
through the use of the treaty-making prerogative. The subjects upon
which Congress may legislate are limited by specific enumeration. The
treaty-making power, however, is not thus limited. Treaties may cover
any subject. It follows that while the Federal Government has no power
(for example) to regulate the descent of real property in the various
states the treaty-making power permits it, by treaties with foreign
nations, to destroy the alienage laws of the states.[1] Another very
recent example is afforded by the Migratory Bird Treaty with Great
Britain.[2] One will search the Constitution in vain for any grant of
power to the Federal Government to enact game laws. Nevertheless, under
this treaty, many state game laws have been practically annulled.

[Footnote 1: _Hauenstein v. Lynham_, 100 U.S., 483.]

[Footnote 2: Sustained by the Supreme Court in _Missouri v. Holland_,
252 U.S., 416.]

But the most far-reaching method by which federal power under the
Constitution has been extended has been the adaptation--some will say
the perversion--by Congress of old grants of power to new ends. Under
the spur of public sentiment Congress has discovered new legislative
possibilities in familiar clauses of the Constitution as one discovers
new beauties in a familiar landscape. The clause offering the greatest
possibilities has been the so-called Commerce Clause, which grants to
Congress power "to regulate commerce with foreign nations, and among the
several states."[1] Under this grant of power Congress has enacted, and
the courts have upheld, a great mass of social and economic legislation
having to do only remotely with commerce. For example, the Sherman Act