restrictions that are different from state law. For example, California and other states “authorize the use of marijuana for medicinal purposes,” but federal law prohibits that activity. Gonzales v. Raich, 545 U.S. 1, 5, 7-8 (2005). Medicinal marijuana users in California and elsewhere could be using marijuana legally under state law, but still be vulnerable to federal prosecution. Similarly, Pendleton was not required to register under Delaware law, but was still vulnerable to federal prosecution for failing to register. In Shenandoah, moreover, the defendant argued that SORNA did not apply to him because New York and Pennsylvania, the two states in which the government alleged that Shenandoah was required to register, had not yet implemented SORNA. We rejected that argument and concluded that “an independent and federally enforceable duty is placed on sex offenders to register.” Shenandoah, 595 F.3d at 157. Even if New York and Pennsylvania never implemented SORNA, such “failure to implement a federal law . . . [would] not give sex offenders a reason to disregard their federal obligation to update their state registrations.” Id. Instead, “[w]hen a sex offender travels in interstate commerce and disobeys the federal command to keep his or her registration current, as required by SORNA, he or she is subject to prosecution.” Id.; see also United States v. Guzman, 591 F.3d 83, 93 (2d Cir. 2010) (“SORNA creates a federal duty to register with the relevant existing state registries regardless of state implementation of the specific additional requirements of SORNA.”).  Put simply, Pendleton‟s federal duty to register under SORNA was not dependent upon his duty to register under Delaware law. A person of ordinary intelligence would not assume that as long as he or she complied with state law on a particular issue, there would be no risk of running afoul of federal law. We therefore reject Pendleton‟s argument as to fair notice under the Due Process Clause. C. Commerce Clause