Dormant Commerce Clause

The "dormant" Commerce Clause, also known as the "negative" Commerce Clause, is a legal doctrine that courts in the United States have inferred from the Commerce Clause in Article I of the United States Constitution. The Commerce Clause expressly grants Congress the power to regulate commerce "among the several states." The idea behind the dormant Commerce Clause is that this grant of power implies a negative converse—a restriction prohibiting a state from passing legislation that improperly burdens or discriminates against interstate commerce. The restriction is self-executing and applies even in the absence of a conflict between state and federal statutes, but Congress may allow states to pass legislation that would otherwise be forbidden by the dormant Commerce Clause.

The premise of the doctrine is that the U.S. Constitution reserves for the United States Congress at least some degree of exclusive federal power "to regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes" (Article I, § 8). Therefore, individual states are limited in their ability to legislate on such matters. The dormant Commerce Clause does not expressly exist in the text of the United States Constitution. It is, rather, a doctrine deduced by the U.S. Supreme Court and lower courts from the actual Commerce Clause of the Constitution.

The idea that regulation of interstate commerce may to some extent be an exclusive Federal power was discussed even before adoption of the Constitution, though the framers did not use the word "dormant." On September 15, 1787, the Framers of the Constitution debated in Philadelphia whether to guarantee states the ability to lay duties of tonnage without Congressional interference, in order for states to finance the clearing of harbors and the building of lighthouses.James Madison believed that the mere existence of the Commerce Clause would bar states from imposing any duty of tonnage: "He was more and more convinced that the regulation of Commerce was in its nature indivisible and ought to be wholly under one authority."

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