<p>Thirty years of modern competition law systems in Central and Eastern Europe invite reflection on the lessons that the region can offer to the world. This paper focuses on the enforcement of the prohibition of anticompetitive agreements: in particular on collusion that involves trade associations. It offers a unique perspective that is aimed at understanding the role of trade associations in shaping the competitive landscape in transition countries and the implications for a European-wide setting. Taking the legacy of the socialist economy as a contextual factor, we show that trade associations may act as a vehicle for perpetuating doing business the old way: according to the cooperation -- rather than the competitive -- paradigm. In parallel, our study is useful to understand -- in the context of enforcement of against trade associations -- the interactions between public interest values and the protection of competition. The paper analyzes the enforcement of competition law in five EU Member States in the region -- Croatia; Czechia; Poland; Romania; and Slovakia, in the period from 2010 to 2020. The paper’s primary research material consists of decisions from national competition authorities and their annual reports. The notion of trade associations is understood broadly in the paper, and professional associations such as bar associations are within the scope of this article.</p>