Federal statute that criminalized the interstate movement of women for prostitution or other immoral purposes.

Congress enacted the Mann Act in 1910 to comply with an international treaty prohibiting the movement of prostitutes between nations and to respond to domestic hysteria that a conspiracy of coerced prostitution, so-called “white slavery,” was flourishing in U.S. cities. It prohibited the interstate transportation of women for “prostitution or debauchery, or for any other immoral purpose.” The legislative history is clear beyond serious argument that Congress did not intend the law to address premarital sex or extramarital affairs, not commercial in nature, that involved a woman crossing a state line.Interstate commerce

In Hoke v. United States[case]Hoke v. United States[Hoke v. United States] (1913), the Supreme Court upheld the constitutionality of the statute against a charge that it exceeded the power of the federal government under the interstate commerce clause. Viewed with the hindsight of history, this was a modest expansion of federal power; far greater was yet to come.

Caminetti v. United States[case]Caminetti v. United States[Caminetti v. United States] (1917) is the best known of the Mann Act cases to come before the Court. Two couples, in extramarital but totally noncommercial relationships, traveled from California to Nevada and were charged with violating the act. The defendants pointed to the legislative history of the statute and argued that the law was intended to criminalize the transportation of prostitutes only. The Court rejected this means of interpretation and declared that it would look only to the plain meaning of the statute. “Immoral purpose” had to mean something beyond prostitution; an extramarital relationship was “immoral,” and therefore, the male defendants were guilty.

Although the Court occasionally revisited the Mann Act and further refined its meaning, Hoke and Caminetti are the most significant cases. During the 1910’s and 1920’s the act was vigorously enforced, especially in noncommercial interstate travel involving unmarried couples. As American mores changed, it was increasingly used to combat prostitution, its original purpose. Ultimately in 1986 Congress amended the law, changing the prohibition to apply to interstate transportation of women for prostitution or any other sexual activity that is punishable by law. Interstate travel involving legal, noncommercial sexual activity was no longer a federal felony.

• Langum, David J. Crossing Over the Line: Legislating Morality and the Mann Act. Chicago: University of Chicago Press, 1994.

Champion v. Ames

Commerce, regulation of

Constitutional interpretation

Progressivism