In a series of groundbreaking articles published over the past fifteen years, James Gardner has led the charge to make state constitutionalism a part of the constitutional law discussion more generally. His new book, Interpreting State Constitutions: A Jurisprudence of Function in a Federal System, steps beyond his study of specific issues in state constitutionalism to lay out an ambitious theory about how state constitutions should be interpreted based on their function within a federal system. Gardner's book is a significant scholarly effort to take state constitutions seriously, in a way that transcends any one jurisdiction or constitutional provision. Gardner's effort solves the puzzle of state constitutions by positioning them within federalism, in contrast to others who see state constitutions as largely independent of the federal constitution or as meriting primacy as their own interpretive texts. He gives "an account of state constitutional interpretation that takes into consideration the way that state power is actually allocated and exercised within the American federal system. In this review, I will summarize Gardner's argument, positioning it within the larger debate about state constitutional interpretation and federalism. As Gardner suggests, understanding state constitutions within the larger national system challenges theorists to focus on the function that state constitutions, and subnational constitutions more generally, perform within a national system. Gardner argues that a functional approach licenses courts to interpret state constitutions instrumentally to facilitate state resistance to national power. His concluding chapter endorses a rebuttable presumption that state judicial power to resist federal authority ought to be construed broadly, envisioning a bolder role than alternative theories for state courts in promoting federalism. After summarizing Gardner's approach, I will discuss two possible objections to it.