statutory purpose clearly and explicitly set forth in 42 USCS§ 16901 was effectuated when sex offenders fell outside purview of 42 USCS § 16913(b). United States v Mason (2007, MD Fla) 510 F Supp 2d 923 (criticized in United States v Muzio (2007, ED Mo) 2007 US Dist LEXIS 54330) and (criticized in United States v Co