Abstract This article examines the legal concept of ‘international organization’ by analysing its functions across public international law, institutional law and domestic law. It demonstrates how the concept structures legal reasoning by articulating a category of international legal subjects and serving as a shorthand for the rules governing the acquisition of status and the legal consequences flowing from that status for members of the category. In doing so, the article discusses which elements are essential, what is at stake in adopting definitions of international organizations and how institutional and domestic law may borrow from the concept as it exists in public international law.
Fernando Lusa Bordin (2026) studied this question.