Global constitutionalism, an idea neither necessarily rooted in nor emerging specifically from international law, has captured the imagination of public international lawyers. Rather than adding to the plethora of suggestions of what a global constitution would and should look like, this article is about why international lawyers are interested in this idea. The literature so far has largely omitted a stocktaking of what it is that is so appealing about constitutionalism and who is particularly partial to it. When discussing global constitutionalism, international lawyers commonly assume one of two orientations: either a normative orientation (this is the type of constitutionalism we should have) or a descriptive orientation (this is the type of constitutionalism we already have). The former mostly concerns visions for “a global constitution” while the latter often concerns ideas of the process that will at some point culminate in “a global constitution;” this process is commonly referred to as “constitutionalization.” The recent co-authored book by Jan Klabbers, Anne Peters and Geir Ulfstein, The Constitutionalization of International Law, sets out to go further. It aims to see “what a constitutional international legal order could look like.” In a sense, they have therefore adopted a third orientation: one that takes the descriptive case of constitutionalism as a given and theorizes about further normative aspects in regard to the international legal order.