SCOTUS has already ruled ex post facto sex offenders rules are Unconstitutional when they refused to over turn the 6th circuit ruling on sex offender registry ex post facto laws (Doe v. Snyder). https://www.washingtonpost.com/news/volokh-conspiracy/wp/2016/09/07/sex-offender-laws-and-the-6th-circuits-ex-post-facto-clause-ruling/?utm_term=.2f73533611a5