Contestations over justice and equity in international environmental regimes present striking evidence of the struggle to create institutions for global environmental governance that are based on widely shared ethical standards of responsibility and accountability. Focusing on two key equity norms—the common heritage of mankind (CHM) and common but differentiated responsibility (CDR)—this paper highlights four factors that affect the influence of moral responsibility norms in global environmental regimes: (i) source and force of articulation, (ii) nature of issue-area, (iii) “moral temper” of the international community, and (iv) “fitness” of norms with the prevailing neoliberal economic idea and structure. Consequent upon the argument that the most important of all these factors is the “fitness” with the extant neoliberal order, the paper questions the assumptions of the burgeoning constructivist scholarship that tends to overemphasize the independent role of intersubjective beliefs in international poli...