Any discussion of the most fundamental of political decisions has to reckon with the towering figure of the German legal theorist, and jurist for the Nazi regime, Carl Schmitt. Schmitt is widely thought to have shown that emergencies pose a profound challenge to the principles of liberal constitutionalism. But what happens when liberal regimes such as that of the United States face emergencies that appear to demand the suspension of legal rules? By definition, there can be no constitutional rule that governs the decision on when to suspend constitutional rules, since such a paradoxical rule—a rule that gives authority to abolish the rules—would likely compromise the very idea of a liberal constitutional order. Schmitt believed that liberals were evasive on this issue: their efforts to avoid the problem of the decision on the exception, he charged, led them to either normalize exceptions to the rule of law or to deny there could be such existential dilemmas for the state. Many scholars who are sympathetic to the cause of constitutional democracy are nonetheless convinced by Schmitt’s critique of the weaknesses of ‘legal liberalism’. The chapters in Part I of this volume address Schmitt’s thought and its implications for American political and constitutional history. The chapters in Part II take up a series of case studies of the theory and practice of emergency powers in American history.