The wording of human rights treaty provisions can be characterised as vague. Consequently, interpretation is particularly important when applying human rights to actual cases. This chapter discusses seven interpretative techniques on which the regional Courts rely and compares how their operationalisation by these Courts enhances or diminishes their legitimacy. Legitimacy is defined here as diffuse support for a Court among the states parties to a regional human rights treaty. The chapter demonstrates that the Courts have much in common by relying on considerations of effectiveness and on an evolutive, autonomous and systemic interpretation. However, their approaches, particularly those of the ECtHR and the IACtHR, differ in important respects as well. Whereas domestic laws are an important source for the former when interpreting the ECHR, the IACtHR and the ACtHPR rely more heavily on international human rights law. Additionally, whereas the ECtHR leaves some room for the states parties to make their own decisions, the IACtHR’s pro persona approach leads it to emphasise the responsibilities of states. These differences make it easier for the ECtHR to address legitimacy challenges compared to the IACtHR.