Over the past decades, large online platforms have gained a powerful (economic) position, potentially disrupting society and the economy. In the EU, several legal instruments may curb this power. These frameworks do not apply in isolation but interrelate, particularly due to (i) the monetisation of personal data and (ii) the introduction of novel regulatory instruments, such as the Digital Markets Act. As a result of this interplay, a complex ‘puzzle’ has materialised in the regulation of personal data markets, in which the competences of enforcers across legal branches and jurisdictions increasingly overlap. This PhD analyses the overlapping competences of enforcers of competition law, the DMA and the GDPR in the context of personal data market, considering the legal orders of the EU, Germany and the Netherlands. Ultimately, the monograph aims to assess the extent to which existing institutional frameworks and cooperation mechanisms can guarantee the coherent application of competition law, the DMA and the GDPR to personal data markets. The question of ‘who should do what’ in addressing the issue of harmful platform power is central to the analysis.
Belle Beems (1994) obtained her Bachelor’s degree (cum laude) at Utrecht University and holds a (cum laude) Master’s degree in European Law from the same university. During her Bachelor’s, she studied for one semester at University College Dublin. Before joining Radboud University, Belle worked as a lecturer and junior researcher at KU Leuven and Utrecht University. During her PhD, she undertook research stays at Pompeu Fabra University in Barcelona, Heinrich Heine University in Düsseldorf and the Vienna University of Economics and Business. Belle contributed to several courses at Radboud’s Department of International and European law focussed on internal market and competition law. Belle published on various topics related to EU law, competition law and data protection law in several national and international peer-reviewed journals, including the European Competition Journal, SEW, the Competition Law Review and the European Data Protection Law Review. Furthermore, she served as a board member of the Dutch Association for European Law (NVER). As of October 2025, Belle is affiliated with Leiden University as an assistant professor.