[1] The practice, introduced by the Adam Walsh Child Protection and Safety Act, was upheld against a challenge that it fell outside the enumerated powers granted to Congress by the Constitution.

The decision did not rule on any other aspect of the law's constitutionality, because only the particular issue of Congressional authority was properly before the Court.

The law that Attorney General Gonzales was applying was ruled unconstitutional by lower courts on the grounds it exceeded Congress’s constitutional authority.

Argued in January 2010 by Solicitor General Elena Kagan, the position of the United States was that the Necessary and Proper Clause gave Congress the power to enact the law.

[9] Stephen Breyer delivered the opinion of the Court, which decided that the Necessary and Proper Clause permitted Congress to enact such a provision.