This chapter comments on the arguments advanced by Steven G. Calabresi and Lucy D. Bickford regarding the principle of subsidiarity as it relates to the European Union's quasi-federal system and the United States's constitutional system. It first questions the aptness of the U.S.-EU comparison and the conception of subsidiarity as being primarily about externalities, with particular emphasis on the problem of “bricolage” and constitutional multifunctionalism. It then notes the lack of a basis in comparative experience for strong judicially enforced versions of subsidiarity and goes on to propose an alternative “proceduralist” approach to the judiciary's role in advancing subsidiarity in the U.S. constitutional context. It also looks at the Warren Court and how it reinforced federalism by nationalizing the Bill of Rights in the U.S. Constitution, thus dramatically improving the legitimacy and efficacy of state governments.