The disagreement between Scalia and the Rehnquist-O’Connor-Thomas dissent in this case is highly nuanced and lawyerly. The dissenters would, as Mark Levin notes, essentially throw out a long (and highly questionable) line of Commerce Clause cases that permit Congress to regulate personal growth and consumption of a product (without any sale into interstate commerce), where that activity would substantially affect interstate commerce. Basically, as Jonathan and Mark note, it is hard to see how the personal consumption of marijuana grown in one’s own backyard has an effect on interstate commerce. But Justice Scalia sees it differently, invoking the “Necessary and Proper” clause of the constitution and concluding that Congress can regulate this growth because the regulation is necessary to make effective a much broader scheme of federal regulation of marijuana sales and distribution. Whatever one’s view of federal drug laws, this is an interesting debate about federal power.