The 'power to regulate commerce,' here meant to be granted, was that power to regulate commerce which previously existed in the States. But what was that power? The States were, unquestionably, supreme; and each possessed that power over commerce, which is acknowledged to reside in every sovereign State. The definition and limits of that power are to be sought among the features of international law; and, as it was not only admitted, but insisted on by both parties, in argument, that, 'unaffected by a state of war, by treaties, or by municipal regulations, all commerce among independent States was legitimate,' there is no necessity to appeal to the oracles of the jus commune for the correctness of that doctrine. The law of nations, regarding man as a social animal, pronounces all commerce legitimate in a state of peace, until prohibited by positive law. The power of a sovereign state over commerce, therefore, amounts to nothing more than a power to limit and restrain it at pleasure. And since the power to prescribe the limits to its freedom, necessarily implies the power to determine what shall remain unrestrained, it follows, that the power must be exclusive; it can reside but in one potentate; and hence, the grant of this power carries with it the whole subject, leaving nothing for the State to act upon.
-- Gibbons v Ogden, 22 U.S. 1 (1824)
This landmark case was decided in Chief Justice (and Founding Father) John Marshall's U.S. Supreme Court.
http://www.capmag.com/article.asp?ID=3295
Restrain?! Why didn't the Supreme Court appointments of Thomas Jefferson and James Madison realize that prohibitions are unconstimatushunal!