アメリカ合衆国憲法修正第13条
The Thirteenth Amendment to the United States Constitution makes involuntary servitude illegal under any U.S. jurisdiction whether at the hands of the government or in the private sphere, except as punishment for a crime: Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction.