You make the same argument as the Pacific Legal Foundation. However, this is contrary to the law, sparse as it is, on the Thirteenth Amendment. Consent is not as to the “act” which leads to the labor, but to the labor itself. Thus, even if someone “voluntarily” enters an agreement to work off the debt of someone who paid their criminal fine, forcing them to perform that labor still violates the Thirteenth Amendmant. See, U.S. v. Reynolds, 235 U.S. 133 (1914). Even if someone receives an advance payment for an agreement to work, they cannot be forced to perform that labor without violating the Thirteenth Amendment. See Pollock v. Williams, 322 U.S. 4 (1944); Taylor v. Georgia, 315 U.S. 25 (1942); Bailey v. Alabama, 219 U.S. 219 (1911).

It is the labor itself which must be voluntary, not the acts or agreements which lead to the labor, i.e., whether “the victim had no available choice but to work or be subject to legal sanction.” United States v. Kozminski, 487 U.S. 931, 943 (1988). Otherwise, one can say that the “voluntary” act of travelling through an area in Africa known to be infested with slave-hunters lead to the “natural result” of being carried off in a slave ship.