D was convicted in a Mississippi court for gratification of lust, a sex offense. D was sentenced to eight years in prison, four years suspended. Prior to his release in May 1999, D signed an Acknowledgment of Convicted Sex Offender's Duty to Register under Mississippi law. In 2002 and 2004, D signed two additional Mississippi state forms acknowledging his duty to register. In 2005, D moved from Mississippi to Iowa and signed Iowa's Sex Offender Registry Notification of Registration Requirement form. In January 2008, Johnson returned to Mississippi and failed to register as a sex offender with the State of Mississippi. D was indicted for violating 18 U.S.C. § 2250(a) by traveling in interstate commerce and knowingly failing to register and update a registration in accordance with SORNA. SORNA was enacted in July 2006. The Attorney General issued an interim regulation stating that SORNA's requirements 'apply to all sex-offenders, including sex offenders convicted of the offense for which registration is required prior to the enactment of that Act.' The regulation was issued without a notice-and-comment period and without a thirty-day waiting period, both of which are mandated by the Administrative Procedure Act. The Attorney General relied upon the good cause exception in the APA to excuse the lack of notice-and-comment and waiting period. The Attorney General cited public safety. The rule took immediate effect. The Attorney General received public comments on SORNA's retroactivity after the fact and responded to those comments in the publication of the final SORNA regulations, which were issued and made effective on July 2, 2008. D plead guilty and reserved his right to appeal on Constitutional grounds. D appealed his conviction.