This article takes the example of cultural tourism to highlight the specificities of European Cultural Policies. It argues, that, although it is often presented as a way of supporting a diversity of approaches, styles and objectives, the subsidiarity principle can sometimes endanger the cultural diversity it seeks to protect. Tourism for instance, has long been considered as a self-regulating activity and cultural tourism is often seen as ‘sustainable by nature’. Experience however shows that local authorities often lack an understanding of all the intricacies and consequences of cultural tourism development. Without proper tools for assessing and preventing negative impacts, local actors may lose control over its development, miss on benefits and endanger the diversity of cultures currently existing and co-existing in the European Union.