Managing Security Exception Claims in International Economic Law: Lessons from Constitutional Theory. In international economic law as well as in domestic law, there is a separation between ordinary commercial relations from exceptional circumstances threatening the essential security interests of a state. Yet, as repetitively evidenced in history, the boundary between the norm and the exception is hard to manage, especially as national security and international trade and investment are deeply intertwined. In international trade and investment law, as more disputes are arising from security-driven measures, adjudicators are increasingly exposed to the dilemma between the need to respect states’ essential sovereign power to defend their national security, on the one hand, and the commitment to the rule of law, on the other. Despite the fundamental importance of this matter, solutions remain uncertain and undertheorized. The same dilemma is confronted by constitutional lawyers. Given the paucity of theoretical accounts of security exceptions in international economic law and rich experience in constitutional law, there is an apparent value for international lawyers to learn from the models and theories on security powers developed in constitutional law. Moreover, the link between domestic law and international economic law on security exceptions is more than one of analogy. The exercise of emergency powers in the economic sphere, e.g. in tackling economic crises, imposing economic sanctions, or in wartime emergency, has triggered litigations and scholarly debates both in domestic constitutional law and in international trade and investment law. My research will first examine the interconnection between international economic law and constitutional law on security exceptions through a historical analysis. It will further draw upon constitutional theory with a view to developing a theoretical model for addressing security exceptions in international economic law.