"The growth of federal power and programs over this century -- involving the regulation of business, the expansion of "civil rights," the production of environmental goods, and much else -- has taken place in large measure through the power of Congress to regulate "commerce among the states." That power has been read so broadly by the modern Court that Congress today can regulate anything that even "affects" commerce, which in principle is everything. As a result, save for the restraints imposed by the Bill of Rights, the commerce power is now essentially plenary, which is hardly what the Framers intended when they enumerated Congress’s powers. Indeed, if they had meant for Congress to be able to do anything it wanted under the commerce power, the enumeration of Congress’s other powers -- to say nothing of the defense of the doctrine of enumerated powers throughout the Federalist Papers -- would have been pointless. The purpose of the commerce clause quite simply, was to enable Congress to ensure the free flow of commerce among the states. Under the Articles of Confederation, state legislatures had enacted tariffs and other protectionist measures that impeded interstate commerce. To break the logjam, Congress was empowered to make commerce among the states "regular." In fact, the need to do so was one of the principal reasons behind the call for a new constitution."
Vice President for Legal Affairs for the Cato Institute
Restoring Constitutional Government, Cato's Letter #9, p. 6, published by the Cato Institute (1995).