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The Second Commerce Clause – Introduction

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The Second Commerce Clause

Philip Hamburger

Columbia University – Law School


The Commerce Clause has long figured as the only commerce clause in the United State Constitution. It is, indeed, THE Commerce Clause. Nonetheless, it has a doppelgänger — another commerce clause that inconspicuously shadows the first and reveals its outlines with unexpected clarity. And this second Commerce Clause is particularly interesting because it calls into doubt the doctrine on the so-called “dormant Commerce Clause.”

The Second Commerce Clause – Introduction

It is well known how the Supreme Court developed doctrine on the non-use or dormancy of the Commerce Clause to counteract discriminatory state regulation of commerce.1 What is less familiar is how the Constitution itself already responded to the discriminatory regulation of commerce in a second Commerce Clause, providing that “No Preference shall be given by any Regulation of Commerce or Revenue to the Ports of one State over those of another.”

The dormant Commerce Clause doctrine is dubious enough on account of the text of the first Commerce Clause. The second Commerce Clause confirms the textual doubts about the dormant Commerce Clause by showing that when the Constitution sought to limit discrimination in the regulation of commerce, it did so expressly, not by implication. The second Commerce Clause, moreover, points to a structural critique, for it reveals that the Constitution responded to discrimination in the regulation of commerce with two mechanisms: in the first Commerce Clause with congressional power to regulate commerce, and only in the second with a constitutional prohibition on discrimination in the regulation of commerce. The First Commerce Clause. –In the Constitution’s initial Commerce Clause, the people of the United States grant Congress the power to “regulate Commerce . . .among the several States.” As recognized by the Supreme Court, this clause gives power to Congress. According to the Court, however, even when Congress does not xercise its power under this clause, the clause by itself bars the states, in their regulations of commerce, from discriminating against other states. The Court draws this conclusion from the Constitution’s unexercised or “dormant” grant of power to Congress, this being how the dormant Commerce Clause doctrine came to enjoy its curious name.

Of course, it may be questioned how, in the absence of congressional legislation, the Commerce Clause—a mere grant of power to Congress—can limit the power of the states. If the grant of power to Congress had been exclusive, it would have deprived the states of all power to regulate commerce among the states. (Under the contemporary interpretation of the Commerce Clause, moreover, if the grant of power were exclusive, it would deprive states of their power to regulate commerce even within their borders.) Yet nothing in the Commerce Clause indicates it is exclusive. Nor does the dormant Commerce Clause doctrine suggest as much.

Indeed, the structure of the Constitution suggests that the Commerce Clause is located in a section that does not limit the states at all. Article I of the Constitution vests all legislative powers of the United States in Congress, and the eighth section of this article enumerates the powers of Congress, including the power to regulate commerce among the states. The ninth section then refines the enumeration of these powers by placing limits on Congress. Only in the following section—the tenth—does the Constitution enumerate limits on the states, especially limits on the power of the states to regulate some of the matters that the eighth section grants to Congress. Revealingly, however, this tenth section—even in its provision barring states from laying imposts or duties on imports or exports—does not prohibit the states from discriminating in the regulation of commerce.

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