The United Nations Through a Separation of Powers Lens

This chapter examines the applicability of the separation of powers (SoP) doctrine to the United Nations (UN), challenging the prevailing assumption that SoP is irrelevant to this international organization. While the UN Charter does not explicitly reference SoP and its institutional design diverges from domestic models, the Charter nonetheless establishes distinct organs with differentiated authority that broadly resemble executive, legislative, and judicial functions. Drawing on Jeremy Waldron’s functional understanding of SoP as a principle for safeguarding the rule of law, we argue that applying this lens to the UN offers valuable insights. First, it underscores the Charter’s structural commitment to legality and the complementary roles of the Security Council, General Assembly, and International Court of Justice. Second, it provides a heuristic for identifying moments when the rule of law is at risk due to authority shifts among these organs. Third, it reveals that tensions arising from such shifts mirror debates familiar in domestic contexts. Through an analysis of three historical periods, we trace patterns of contraction, expansion, and transgression of authority within the UN system, concluding with reflections on implications for UN reform and the rule of law in international governance.