Challenging the myth that the federal government exercises exclusive control over U.S. foreign-policymaking, Michael J. Glennon and Robert D. Sloane propose that we recognize the prominent role that states and cities now play in that realm. Foreign Affairs Federalism provides the first comprehensive study of the constitutional law and practice of federalism in the conduct of U.S. foreign relations. It could hardly be timelier. States and cities recently have limited greenhouse gas emissions, declared nuclear free zones and sanctuaries for undocumented immigrants, established...