Commerce Clause. The District Court, in United States v. Guzman, had held that 42 U.SC. 16913, which provides that a convicted sex offender must register "and keep the registration current, in each jurisdiction where the offender resides, . . is . . . employ[ed], [or] is a student," exceeds congressional power under the Commerce Clause. The Second Circuit disagreed, holding that "[t]o the extent that [section] 16913 regulates solely intrastate activity, its means 'are "reasonably adapted" to teh attainmnet of a legitimate end under the commerce power.'"

The decision can be found here.