In Hoke v. United States, the Supreme Court held the Mann Act as Constitution, the act prohibited the interstate transportation of women for ‘immoral’ purposes. The suit was brought by one Effie Hoke who had been convicted under the law on the charge that she enticed a woman to cross interstate boundaries for the purpose of prostitution.
The issue raised in this case was whether or not the Act violated the Commerce Clause.
Writing for a unanimous Supreme Court, Justice McKenna ruled that it did not.
The ruling in this case was significant because it stressed that Congress does have police powers if the activity being regulated is involved in interstate commerce. Because police powers had previously been considered exclusive state powers, this ruling allotted more powers to Congress.