Democratic accountability v. technical expertise in (EU) competition law proceedings KJ Cseres, Procedures and, in particular, administrative procedures are the foundation of efficient and legitimate modern democratic polity. Procedural frameworks are essential for the effective implementation, application and enforcement of law. In modern administration, the administrative decision-maker needs to be equipped with discretionary decision-making powers in order to address and efficiently solve complex socio-economic, technical and scientific problems. Still, administrative procedures are not just featured by expert driven regulatory competence, but also require democratic legitimacy. Hence, administrative procedures are underlined by the dichotomy between efficiency and procedural justice that ensures transparency and accountability. This means on the one hand, the need for efficient expertise driven technocratic decision-making to serve markets and consumers, and on the other hand, the democratic rationale of participatory model of administrative decision-making that involves general procedural rules for citizens’ participation. In this talk I will investigate the role third parties (all natural and legal persons other than the undertakings under investigation) can and should play in (EU) competition law proceedings. Competition law is one example of complex, fast-changing technical areas of the modern regulatory state that requires open-ended procedures and wide margin of discretion on the side of the administrative decision-maker for effective enforcement. Administrative procedures for the enforcement of (EU) competition law have been conceived along a strictly bilateral scheme and gravitate around the relationship that opposes the competition authority (eg Commission) and the undertaking targeted by its investigations. All other natural or legal persons who are concerned by the procedure intervene in different procedural qualities. They are third parties who do not need to defend their personal legal sphere, since the procedure has not been initiated against them. They do not intervene in the quality of defendants, still, they have an interest in its outcome: the ensuing decisions might affect their economic interests, even if not always in a direct way. By critically reflecting on recent legislation, such as the DMA and a proposal by the EU Commission to abolish formal complaints for the enforcement of Articles 101 and 102 TFEU, I will argue that third parties are not merely important “watchdogs” who can assist competition authorities in monitoring the good functioning of markets, but their participation in administrative procedures is an important aspect of transparency and accountability that enhances the legitimacy of the proceedings and the final decision making. Third parties’ participation functions as a complement to judicial review, because third parties are given the opportunity to contradict the possible decision of the competition authority, invoking errors, flaws, or mistakes which could ultimately lead to the illegality of the final decision.