13th Amendment
SECTION 1. 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.SECTION 2. Congress shall have power to enforce this article by appropriate legislation.
Check out the Petition for Renunciation of United States Citizenship by Brothers Incarcerated in the Comstock Correctional Facility