Abstract:The surge of interest among international lawyers in "constitutionalism" represents one of several efforts to reconceptualize international governance; others include the research projects on global administrative law and legalization. The paper applies the constitutionalist lens to international environmental law - one of the few fields of international law to which constitutionalist modes of analysis have not yet been applied. Given the protean quality of the terms "constitution" and "constitutionalism," the paper begins by unpacking these concepts. By disaggregating these concepts into a number of separate variables, which have a more determinate, unambiguous meaning, we can answer the question, "is there an international environmental constitution?", in a more nuanced way - not in an all or nothing fashion, but by considering the extent to which international environmental law has constitutional dimensions. The paper concludes that, although individual treaty regimes have constitutional features, international environmental law as a whole lacks the hallmarks of a constitutional order.