Since the beginning of the new millennium, municipal cooperations have come into the focus of European public procurement law. This has given rise to controversial discussions and legal uncertainty. Even the long-awaited ruling by the ECJ in the case of Stadtreinigung Hamburg from 2009 did not provide a definitive answer to the question of whether and when municipal collaborations are subject to tendering. The aim of this work is to find a balance between the communal organizational and cooperation sovereignty and the interests of the private sector and European competition law and to offer a dogmatically viable and practically convincing solution to the question of the obligation to tender for communal cooperations. The author chooses the provision of Art. 106 (2) TFEU as the main approach; The previous jurisprudence and literature, the procurement and municipal law principles as well as the innovations at European level through the Lisbon Treaty are taken into account.