Under the Fifth Amendment prohibition of Ex Post Facto Laws, a person should not be subjected to a criminal punishment or convicted of breaking a law if that law was not in place at the time of the commission of the act. Because the convicted sex offender committed his crime at a time when he/she could not have possibly been aware of the potential requirement to register upon release from prison, he/she should not be subjected to the requirements of this law.
However, the Supreme Court has already determined that sex offender registration is not a punishment that was contemplated by the Framers of the Constitution and upheld similar legislation in Alaska in 2003.