In 2005 the Supreme Court said the federal government's power to "regulate commerce…among the several states" extends to the tiniest speck of marijuana wherever it may be found, even in the home of a patient who grows it for her own medical use in compliance with state law. "If Congress can regulate this under the Commerce Clause," Justice Clarence Thomas warned in his dissent, "then it can regulate virtually anything—and the Federal Government is no longer one of limited and enumerated powers." The Obama administration, which was in court this week defending the new federal requirement that every American obtain...