In Gibbons v. Ogden, the first Supreme Court decision to discuss the Commerce Clause, Chief Justice John Marshall endorsed the notion of a Dormant Commerce Clause but refused to adopt it as constitutional principle. In this article, Professor Norman Williams answers why Marshall hedged on the Dormant Commerce Clause. First, Marshall apprehended the need to provide a comprehensive articulation of the scope of Congress’s affirmative regulatory power under the Commerce Clause. Second, Marshall was wary of inserting the judiciary into another battle regarding the constitutional scope of state authority. This reassessment resolves an otherwise inadequately explained historical puzzle regarding the Marshall Court and sheds light upon contemporary debates regarding popular constitutionalism and the interpretive role of the Supreme Court.