The chapter outlines the feminist social theory and socio-legal methodology that the book uses to examine ‘international justice’. It shows why this sociological framing is crucial for understanding ‘international justice’ as an expression of global social relations and values. The chapter explains how a feminist sociological understanding of ‘international justice’ is developed by studying existing forms of legal and feminist justice. These are exemplified by the International Criminal Tribunal for the former Yugoslavia and the Women’s Court (former Yugoslavia) and their treatment of conflict-related sexual violence. The chapter sets out the building blocks of the feminist social theory of legal and feminist justice, drawing on Marxist, psychoanalytic, and feminist theory. This theory describes these distinctive forms of justice, considers how these forms express historically specific social relations, and analyses whether they reproduce existing social orders or produce new social relations. The chapter also sets out the socio-legal methodology for building this social theory. It explains the socio-legal case study methodology and mixed methods used to study international justice.