EU fundamental rights feature ever more prominently in the case law of the European Court of Justice (CJEU) and continue to attract considerable academic debate. The CJEU has long recognised that these rights have an ‘essence’ that warrants far-reaching protection. The nature, application, and implications of this legal concept remain underdeveloped in the case law and underexplored in the literature, however. This is curious given the potentially significant impact of the concept of essence on the protection of fundamental rights under EU law and the growing intertwinement of the essence of certain rights with the EU’s founding values.

This Dissertation seeks to address the gap in the literature by offering an in-depth discussion of the concept of essence as such and in EU law. It does so in three parts: Firstly, it provides a general legal-theoretical account of the concept that reviews whether the essence of a right enshrines an absolute or relative guarantee. This includes a discussion of the different approaches that could be taken to defining the essence of a given right in practice. The theoretical account lays the foundation for the second part, which analyses how the concept of essence has been understood and applied by the CJEU over the past fifty years. This includes an extensive review of the relevant case law and its subsequent reconstruction in light of the theoretical foundation. This enables the further clarification and systemisation of the Court’s approach. Thirdly and finally, this Dissertation reflects on the role of the concept of essence in EU law more broadly. It shows that the roots of the concept reach deep into the foundations of the EU’s legal system. Essence is not only a guarantee that the fundamental rights of individuals under EU law will remain effective; it is also intertwined with the effective functioning of the EU’s legal system overall.