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Unit: $U54

[10-04-01 09:35:40] PAGES PGT: OPIN

Cite as: 529 U. S. 598 (2000)

617

Opinion of the Court

We accordingly reject the argument that Congress may
regulate noneconomic, violent criminal conduct based solely
on that conduct’s aggregate effect on interstate commerce.
The Constitution requires a distinction between what is

manent and indispensable feature of our constitutional system’ ” that “ ‘the
federal judiciary is supreme in the exposition of the law of the Constitu-
tion.’ ” Miller v. Johnson, 515 U. S. 900, 922–923 (1995) (quoting Cooper
v. Aaron, 358 U. S. 1, 18 (1958)).

No doubt the political branches have a role in interpreting and apply-
ing the Constitution, but ever since Marbury this Court has remained
the ultimate expositor of the constitutional text. As we emphasized in
United States v. Nixon, 418 U. S. 683 (1974): “In the performance of as-
signed constitutional duties each branch of the Government must initially
interpret the Constitution, and the interpretation of its powers by any
branch is due great respect from the others. . . . Many decisions of this
Court, however, have unequivocally reafﬁrmed the holding of Marbury
that ‘[i]t is emphatically the province and duty of the judicial department
to say what the law is.’ ”

Id., at 703 (citation omitted).

Contrary to Justice Souter’s suggestion, see post, at 647–652, and
n. 14, Gibbons did not exempt the commerce power from this cardinal rule
of constitutional law. His assertion that, from Gibbons on, public opinion
has been the only restraint on the congressional exercise of the commerce
power is true only insofar as it contends that political accountability is and
has been the only limit on Congress’ exercise of the commerce power
within that power’s outer bounds. As the language surrounding that re-
lied upon by Justice Souter makes clear, Gibbons did not remove from
this Court the authority to deﬁne that boundary. See Gibbons, supra, at
194–195 (“It is not intended to say that these words comprehend that
commerce, which is completely internal, which is carried on between
man and man in a State, or between different parts of the same State,
and which does not extend to or affect other States. . . . Comprehensive
as the word ‘among’ is, it may very properly be restricted to that com-
merce which concerns more States than one. The phrase is not one which
would probably have been selected to indicate the completely interior
trafﬁc of a State, because it is not an apt phrase for that purpose; and the
enumeration of the particular classes of commerce to which the power was
to be extended, would not have been made, had the intention been to
extend the power to every description. The enumeration presupposes
something not enumerated; and that something, if we regard the language
or the subject of the sentence, must be the exclusively internal commerce
of a State”).