The Commerce Clause serves a two-fold purpose: it is the direct source of the most important powers that the Federal Government exercises in peacetime, and, except for the due process and equal protection clauses of the Fourteenth Amendment, it is the most important limitation imposed by the Constitution on the exercise of state power. The latter, restrictive operation of the clause was long the more important one from the point of view of the constitutional lawyer. Of the approximately 1400 cases that reached the Supreme Court under the clause prior to 1900, the overwhelming proportion stemmed from state legislation.663 The result was that, generally, the guiding lines in construction of the clause were initially laid down in the context of curbing state power rather than in that of its operation as a source of national power. The consequence of this historical progression was that the word “commerce” came to dominate the clause while the word “regulate” remained in the background. The so-called “constitutional revolution” of the 1930s, however, brought the latter word to its present prominence.
