aid: "The power to
regulate commerce among the several States was granted to Congress in
terms as absolute as is the power to regulate commerce with foreign
nations."[333] Today it is firmly established doctrine that the power to
regulate commerce, whether with foreign nations or among the several
States comprises the power to restrain or prohibit it at all times for
the welfare of the public, provided only the specific limitations
imposed upon Congress's powers, as by the due process clause of the
Fifth Amendment, are not transgressed.[334]

Nor does the power to regulate commerce stop with, nor in fact is it
most commonly exercised in, measures designed to outlaw some branch of
commerce. In the words of the Court: It is the power to provide by
appropriate legislation for its "protection and advancement";[335] to
adopt measures "to promote its growth and insure its safety";[336] "to
foster, protect, control and restrain, [commerce]."[337] This
protective power has, moreover, two dimensions. In the first place, it
includes the power to reach and remove every conceivable obstacle to or
restriction upon interstate and foreign commerce from whatever source
arising, whether it results from unfavorable conditions within the
States or from State legislative policy, like the monopoly involved in
Gibbons _v._ Ogden; or from both combined. In the second place, it
extends--as does also the power to restrain commerce--to the instruments
and agents by which commerce is carried on; nor are such instruments and
agents confined to those which were known or in use when the
Constitution was adopted.[338]

INSTRUMENTS OF COMMERCE

The applicability of Congress's power to the agents and instruments of
commerce is implied in Marshall's opinion in Gibbons _v._ Ogden,[339]
where the waters of the State of New York in their quality as highways
of interstate and foreign transportation are held to be governed by the
overruling power of Congress. Likewise, the same opinion recognizes that
in "the progress of things," new and other instruments of commerce will
make their appearance. When the Licensing Act of 1793 was passed, the
only craft to which it could apply were sailing vessels, but it and the
power by which it was enacted were, Marshall asserted, indifferent to
the "principle" by which vessels were moved. Its provisions therefore
reached steam vessels as well. A little over half a century later the
principle embodied in this holding w