The aim of this thesis is to investigate the way in which the Court of Justice of the European Union (CJEU) uses the margin of discretion-technique to adjudicate cases involving fundamental rights, and importantly, what this use entails. This thesis will answer these questions by presenting the argument that the margin of discretion-technique opens up discretional spaces in specific instances of adjudication that enable participation of actors from both legal loci, along with their respective readings of legal sources. This creates an adjudicative process that blurs the boundaries between what is a EUropean and what is a nationally defined standard of fundamental rights protection. The margin of discretion-technique therefore promotes euro-national interconnectedness in the formulation of the applicable standard of fundamental rights protection in a given case, rather than separating subject matters and legal conflicts along jurisdictional lines. The presentation of this thesis proceeds as follows. Firstly, the origins of techniques of coordination of overlapping jurisdictions that share commitment to norms, such as margins of discretion, will be investigated and thereafter understood in the context of the European Union. Secondly, three dominant narratives pertaining to discourse on the CJEU's adjudication of fundamental rights will be reconstructed and their reliance on euro-national binary logics will be highlighted. These narratives then serve as points of contrast in what is the main body of the thesis, namely a presentation of three typologies of the CJEU's margins of discretion-use in its case law involving fundamental rights. In contrast to the dominant narratives, these typologies will illustrate the intricate sharing of interpretative authority that the margins of discretion represent, which creates the precondition for an interconnected elaboration of the standard of fundamental rights protection. Lastly, the legal pattern of interconnectedness will be picked apart and understood as a feature of the CJEU's adjudication of fundamental rights.