This chapter introduces the phenomenon of soft law and its use by national courts as an understudied but significant component of European integration through law. It draws key insights from the literature on Europeanization and judicial politics on how EU instruments are transposed to the national level and courts, but also points to their limitations when applied to soft law. Against this background, the chapter defines the primary aim of the book as providing a systematic, comparative, and longitudinal analysis of the judicial use of soft law, addressing the questions: How do courts use soft law? Why do courts use it? And what are the broader effects?