Constitutional interpretation across the globe is taking on an increasingly cosmopolitan character, as comparative jurisprudence comes to assume a central place in constitutional adjudication. The use of comparative jurisprudence raises difficult theoretical question because it stands at odds with one of the dominant understandings of constitutionalism: that the constitution of a nation emerges from, embodies, and aspires to sustain or respond to that nation's particular history and political traditions. Presumptively, then, courts must justify why comparative law should count. In this Article, I argue that the answer to this question lies embedded in the actual practice of comparative constitutional interpretation. Through a discussion of case studies, I claim that comparative jurisprudence is used in three different ways in constitutional adjudication, and that each of these interpretive methodologies, in turn, articulates distinct normative justifications for the use of comparative law. The first interpretive mode, universalist interpretation, holds that constitutional guarantees are cut from a universal cloth. The second mode, genealogical interpretation, holds that constitutions are often tied together by complicated relationships of descent and history, and that those relationships are sufficient justification to import and apply entire areas of constitutional doctrine. In the third mode, dialogical interpretation, courts identify the normative and factual assumptions underlying their own constitutional jurisprudence by engaging with comparable jurisprudence of other jurisdictions. Once the normative skeleton of comparative constitutional interpretation is laid bare, a much needed and long overdue constitutional conversation on this practice can begin. That conversation should revolve around three different issues: the scope of each mode of comparative constitutional interpretation, the effect of each mode on domestic constitutional culture, and the legitimacy of the normative claims that each mode entails. By illustrating how that conversation could unfold, I hope to clarify what is at stake when courts weave comparative jurisprudence into constitutional discourse.