This book chapter explores the Katrina response effort to illustrate the governmental decision-making that operates in the shadow of the interpretive model of federalism in use by courts and policymakers. In the American federal system, citizens are of both the United States and the individual states in which they reside, and subject to the respective laws of each. The Constitution enumerates those powers under which the federal government is authorized to make law, and the states may regulate in any area not preempted by legitimate federal law. Yet the fact that Americans are citizens of two separate sovereigns does not resolve the precise contours of the relationship between the two. Constitutional analysis reveals pockets of textual ambi...