Government ”can exercise only the powers granted to it.”
McCulloch, supra, at 405.
Today, the restrictions on government power foremost in
many Americans’ minds are likely to be affirmative pro-
hibitions, such as contained in the Bill of Rights. These
affirmative prohibitions come into play, however, only where
the Government possesses authority to act in the first
place. If no enumerated power authorizes Congress to
pass a certain law, that law may not be enacted, even if it
would not violate any of the express prohibitions in the
Bill of Rights or elsewhere in the Constitution.
Indeed, the Constitution did not initially include a Bill
of Rights at least partly because the Framers felt the enu-
meration of powers sufficed to restrain the Government.
As Alexander Hamilton put it, ”the Constitution is itself,
in every rational sense, and to every useful purpose,
A BILL OF RIGHTS.” The Federalist No. 84, p. 515 (C. Ros-
siter ed. 1961). And when the Bill of Rights was ratified,
it made express what the enumeration of powers neces-
sarily implied: ”The powers not delegated to the United
States by the Constitution . . . are reserved to the States
respectively, or to the people.” U. S. Const., Amdt. 10.
The Federal Government has expanded dramatically over
the past two centuries, but it still must show that a consti-
tutional grant of power authorizes each of its actions. See,
e.g., United States v. Comstock, 560 U. S. ___ (2010).
The same does not apply to the States, because the Con-
stitution is not the source of their power. The Consti-
tution may restrict state governments-as it does, for
example, by forbidding them to deny any person the equal
protection of the laws. But where such prohibitions do
not apply, state governments do not need constitutional au –
thorization to act. The States thus can and do perform
many of the vital functions of modern government-
punishing street crime, running public schools, and zoning
property for development, to name but a few-even though
the Constitution’s text does not authorize any government
to do so. Our cases refer to this general power of govern-
ing, possessed by the States but not by the Federal Gov-
ernment, as the ”police power.” See, e.g., United States v.
Morrison, 529 U. S. 598, 618-619 (2000).
“State sovereignty is not just an end in itself: Rather,
federalism secures to citizens the liberties that derive from
the diffusion of sovereign power.” New York v. United
States, 505 U. S. 144, 181 (1992) (internal quotation
marks omitted). Because the police power is controlled by
50 different States instead of one national sovereign, the
facets of governing that touch on citizens’ daily lives are
normally administered by smaller governments closer to
the governed. The Framers thus ensured that powers
which “in the ordinary course of affairs, concern the lives,
liberties, and properties of the people” were held by gov-
ernments more local and more accountable than a dis-
tant federal bureaucracy. The Federalist No. 45, at 293
(J. Madison). The independent power of the States also
serves as a check on the power of the Federal Government:
“By denying any one government complete jurisdiction
over all the concerns of public life, federalism protects the
liberty of the individual from arbitrary power.” Bond v.
United States, 564 U. S. ___, ___ (2011) (slip op., at 910).
This case concerns two powers that the Constitution
does grant the Federal Government, but which must be
read carefully to avoid creating a general federal authority
akin to the police power. The Constitution authorizes
Congress to ”regulate Commerce with foreign Nations, and
among the several States, and with the Indian Tribes.”
Art. I, §8, cl. 3. Our precedents read that to mean that
Congress may regulate ”the channels of interstate com-
merce,” “persons or things in interstate commerce,” and
“those activities that substantially affect interstate com-
merce.” Morrison, supra, at 609 (internal quotation marks
omitted). The power over activities that substantially