This article focuses on the concept of just transition, which has recently greatly expanded in the climate debate, expressing the demand to adopt and implement climate policies leading to decarbonisation in a way that maintains equity and justice. Building on previous research on the concept of just transition in other disciplines of social sciences, and on the concept’s appearance in international climate law instruments and law literature, we analyse the just transition in the field of law. We seek to clarify its conceptual framing, to define its meaning, and to determine its position and limits in law. We then examine it vertically (for each level of law) and horizontally, addressing the main criteria that define its content, i.e., human rights and legal principles.