Rethinking the Legitimacy of International Law: Piecemeal or Systemic?

This chapter rethinks the legitimacy of international law by challenging the assumption that legitimate authority must generate a moral duty to obey. It argues instead that legitimacy is better understood as a moral power to impose and enforce institutional obligations, rendering subjects liable to changes in their normative situation, rather than as the source of exclusionary reasons for compliance. The chapter criticizes the dominant service conception for producing a piecemeal account of international legal authority, particularly through subject fragmentation that undermines equality and coordination. Furthermore, it struggles to guide action under conditions of reasonable disagreement and risks entrenching global power asymmetries. By contrast, the power-liability account shifts attention from obligations to obey particular directives to liability to be bound by an institutional order as a whole. This shift supports a systemic and relational approach to legitimacy, on which international legal authority cannot be assessed at the level of individual rules or institutions, but must be evaluated in light of the interdependencies among legal regimes, international institutions, and states. The chapter concludes that recent erosions of multilateralism, human rights protection, and constraints on the use of force point to a deeper legitimacy crisis of the international legal order.