The Thirteenth Amendment to the United States Constitution provides:
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.
Slavery and Involuntary Servitude are distinct concepts. Bailey v. Alabama, 219 US 219, 240 (1911). Slavery refers to one person having absolute power over the life, fortune, and liberty of another. Involuntary Servitude refers to one being forced to labor for another. Black's Law, Seventh Edition.
18 U.S.C. 1584 makes the infliction of involuntary servitude a federal criminal offense punishable by up to 20 years imprisonment. “'[I]nvoluntary servitude' necessarily means a condition of servitude in which the victim is forced to work for the defendant by the use or threat of physical restraint or physical injury, or by the use or threat of coercion through law or the legal process.” United States v. Kozminski, 487 US 931, 952-53 (1988).
Imposing forced labor is also a criminal offense under 18 USC 1589.
Labor is defined as work of any type, including mental exertion. Black's Law, Seventh Edition.