Abstract: The workshop from which this volume emerged reflected in a variety of ways on constitutionalism as a way of thinking about global governance. In the past few years, many have experimented with the metaphor of a constitution to describe the legal order beyond the nation-state. We have been encouraged to think of the UN Charter as a constitution, particularly when it comes to the use of force. Others have seen a constitutional moment in the emergence of human rights as a global vernacular for the legitimacy of power. Some trade scholars have proposed that we see the World Trade Organization (WTO) as a constitutional order. The WTO has rendered the General Agreement on Tariffs and Trade (GATT) more properly legal, strengthening dispute settlement and deepening engagement with national legal regulations. If, as Ernst-Ulrich Petersmann urges, we were to add human rights to what John Jackson famously termed the WTO's substantive legal “interface” between national regulatory systems, we might well see the result as a constitution, at least to the extent that we are willing to see the legal regime of the European Union in constitutional terms. At the same time, others find the key to world public law in the relations among national constitutions. Comparative constitutional law is front and center in their accounts of how we are governed at the global level.