The Role of the Judicial Branch in EU Migration Law. A Separation of Powers Perspective

Abstract

This thesis examines the role of the Court of Justice of the EU in EU migration law through the lens of separation of powers. It rests on the premise that EU democracy benefits from a substantive principle of separation of powers. The separation of powers is being tested in EU migration law. Political actors sometimes circumvent democratic procedures and institutional powers to restrict migration. The externalisation of migration control to third countries removes both parliamentary oversight and judicial review. Moreover, persistent non-compliance by Member States strains the rule of law and threatens the human rights of third-country nationals. The thesis develops a dynamic concept of separation of powers defined by three elements: first, the protection of individual and collective self-determination; second, the structure of institutional relationships and interactions; and, third, mechanisms to manage both cooperation and disagreement. It argues that EU migration law requires not only collaboration but also a stronger element of agonism – understood as constructive contestation – and a judiciary capable of counterbalancing the executive. Through qualitative case analyses and a quantitative study of migration case law from 2010 to 2020, the thesis finds that the CJEU seeks to uphold a functional separation of powers by exercising limited judicial review. This is evident in accommodating interpretations of the EU political institutions’ preferences and a reasoning focused on secondary law. Such restraint does not achieve a balance of power but reinforces a hierarchy among the EU’s three branches. While collaboration can sustain stable institutional relations, the rejection of agonism leaves executive power largely unchecked. When the executive branch undermines the separation of powers and challenges the constitutional values on which the legitimacy of EU migration law rests, the Court’s restraint becomes insufficient to safeguard individual and collective self-determination.