This chapter outlines the research design, data, and methods. Germany and France, as well as state aid and pharmaceutical regulation are selected as the main cases where the use of soft law is likely, but which differ along key comparative dimensions. The chapter then outlines the book’s mixed-methods design: First, patterns of soft law usage are mapped using a judgment database, data from an original survey of judges, and an exploration of a wider set of judgments across countries. Second, these patterns are explained by testing the factors developed in Chapter 2 against the judgment data and survey data in France and Germany. Third, the causal mechanisms leading to the use of soft law in the courts and wider policy effects are traced in four typical case studies in German courts, based on a close reading of judgments in two policy areas and interviews with national actors.