Oh, and check out post #3 of your link. It appears that Founding Father James Madison disagrees with your Mr. Barnett. As does Founding Father and Chief Justice John Marshall's court which said in Gibbons v. Ogden, 22 U.S. 1 (1824):
"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."
"Of all the endless variety of branches of foreign commerce, now carried on to every quarter of the world, I know of no one that is permitted by act of Congress, any otherwise than by not being forbidden. No statute of the United States, that I know of, was ever passed to permit a commerce, unless in consequence of its having been prohibited by some previous statute."