Ex-felon registration laws, and the sex offender registration laws in particular, force ex-felons to help the government maintain a data bank containing the felon's personal information. The government could have retained private business to perform that function but did not do so, the cost would have been enormous. Instead, the government imposed a duty of self-reporting on the individual felon. The courts have held that ex-felon registration laws are not new punishment for an old crime and, therefore, may be retroactively applied without violating the ex post facto clause. E.g., Smith v. Doe. These registration laws, at least initially, implicate the 13th Amendment, which 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
"Labor" is defined as work of any type, including mental exertion. Black's Law. The registration laws extort physical and mental exertion from the individual who is obligated, by the threat of imprisonment, to physically register and live thereafter within the confines of the supplied information, within a 48 hour margin of error.
I submit that the court's determination that the registration laws are not punishment is the very reason they cannot be constitutionally imposed.