This introductory chapter by the editor discusses the goals of the book, introduces the questions central to it as well as develops a methodological framework. It relates to existing scholarship on the impact of human rights law upon other branches of international law and on the fragmentation of international law. It outlines the methodology that was applied in working towards this volume by presenting a range of distinctions that provide conceptual tools for detecting and assessing the different ways how international non-human-rights courts may refer to human rights. These include categories of human rights, sources of human rights norms, and three contexts for their application, namely due process rights applied in the proceedings of the court in question, substantive human rights norms as applicable law or basis for subject-matter jurisdiction, and interpretive reliance on human rights through systemic integration. The chapter also relates to the legitimacy of international courts by showing that how international courts relate to human rights norms matters for factors of legitimacy.