This is an introduction to international law for politics and IR students. What is international law? And what is international justice? This book shows that studying these questions together is essential. Students will develop an understanding of international law and the importance of socio-economic and political factors in shaping its formulation, present development and operations. And they will explore the critical debates on the nature of international justice. In asking what international law is 'for' and what it 'should be', they will engage with some of the most crucial questions of international politics today and examine the detail of sharply divided political opinion on, for example, the nature and justice of humanitarian intervention, the obligations that the rich have towards the global poor and the future of global governance and international legal structures. Each chapter explores a central issue in public international law and IR theory, showing how international law and normative political debate are entwined. It introduces the principles of international law that relate to IR and politics, such as sovereignty and global governance, sovereign & diplomatic immunity, human rights, the use of force, sanctions and the domestic impact of international law. It explains how socio-economic and political factors shape the formulation, development and operation of international law.