We start with first principles. The Constitution creates a Federal Government of enumerated powers. See Art. I, § 8. As James Madison wrote: "The powers delegated by the proposed Constitution to the federal government are few and defined. Those which are to remain in the State governments are numerous and indefinite." The Federalist No. 45, pp. 292-293 (C. Rossiter ed. 1961). This constitutionally mandated division of authority "was adopted by the Framers to ensure protection of our fundamental liberties." Gregory v .Ashcroft, 501 U.S. 452, 458 (1991) (internal quotation marks omitted). "Just as the separation and independence of the coordinate branches of the Federal Government serve to prevent the accumulation of excessive power in any one branch, a healthy balance of power between the States and the Federal Government will reduce the risk of tyranny and abuse from either front." Ibid.
The Constitution delegates to Congress the power "[t]o regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes." Art. I, § 8, cl. 3. The Court, through Chief Justice Marshall, first defined the nature of Congress' commerce power in Gibbons v.Ogden, 9 Wheat. 1, 189-190 (1824):
"Commerce, undoubtedly, is traffic, but it is something more: it is intercourse. It describes the commercial intercourse between nations, and parts of nations, in all its branches, and is regulated by prescribing rules for carrying on that intercourse."
The commerce power "is the power to regulate; that is, to prescribe the rule by which commerce is to be governed. This power, like all others vested in congress, is complete in itself, may be exercised to its utmost extent, and acknowledges no limitations, other than are prescribed in the constitution." Id., at 196. The Gibbons Court, however, acknowledged that limitations on the commerce power are inherent in the very language of the Commerce Clause.