Over at Big Government, Paul Moreno reminds us of the baleful effect of The Mann Act, which turns a century young today this year and helped push along the massive expansion of the federal government via an unrestrained reading of the commerce clause:
The Mann Act was the real beginning of the Bureau of Investigation (later, the F.B.I.), which then used Prohibition to extend its power. The bureau secured five thousand Mann Act convictions in the 1920s. Bureau chief J. Edgar Hoover personally led mass raids, and acquired information that compromised public officials. The act (like the income tax laws) was used to get gangsters who could not otherwise be convicted, and often targeted blacks who traveled with white women (most notably black heavyweight champion Jack Johnson), political dissidents, and other unpopular minorities.
The Mann Act showed how far the federal police power had been extended. Federal power "to regulate commerce among the states" had been extended to moral regulation, and might therefore be extended to any other kind of regulation. This went beyond the attempt to prohibit interstate shipment of things, as Attorney General Philander Knox put it, "noxious or dangerous in themselves," which had heretofore been widely regarded as the limit of the police-power extension of the commerce power. In the Mann Act, there were neither things nor commercial activity involved. Chief Justice John Marshall provided a famous definition of what "commerce among the states" meant in 1824. Commerce, he said, "undoubtedly, is traffic, but it is something more: it is intercourse." Only the most extravagant extension of this definition of commerce could reach cases…of consensual if illicit trysts. After the New Deal swept away the last vestiges of constitutional limitations on Congress' powers, later legislators would not even bother to give pretexts to their attempts to regulate gun possession, domestic violence and, now, health care.
Note: The Mann Act was revised in 1986 to apply only when some sort of criminalized sexual activity is involved, but is still in force.
And watch this Reason.tv video about the commerce clause and its discontents: