Public International Law governs the relations between States and a rapidly increasing number of other subject-matters, comprising everything from commercial interests to human rights, from environmental concerns to war. Although specialized regimes have arisen to address many of these issues within the international legal order, the core of public international law, its nuts and bolts, provides a common set of legal and institutional concepts and rules on which international lawyers routinely rely when advising governments, litigating cases and negotiating treaties across substantive regimes. Building upon the foundations established in Transnational Law, this course explores in greater detail these foundational rules of the public international legal order. The targeted areas will include international legal personality, international law-making, the law of treaties, State responsibility, and the settlement of international disputes. The course will focus on identifying and exploring the role of these ordering rules of public international law across substantive fields of international law such as human rights law, immunities of States and their organs, and the law on the use of force. While students can expect to be exposed to the substantive law of many regimes within public international law, this course will not feature in depth analysis of any of the regimes dealt with in other specialized courses nor will the course duplicate Transnational Law. Rather, by focusing on the perspective of States and international law practitioners, students will develop the capacity to work with the background rules animating the various substantive regimes. For this purpose, the course will also familiarize students with the specific research methods and materials used in public international law practice.