The protected areas are increasingly regarded as open and dynamic social-ecological systems that interact with their environment. Within this context, we focus on Nature Reserves, one of the main French conservation tools. The Nature Reserve of France Association (RNF in French) coordinates Nature Reserves’ managers. RNF is at once a national network of protected natural areas, an information centre that focuses on the sharing of managers’ professional experiences and also a dedicated lobbying agency. RNF occupies today a key place in the institutional scene of Nature protection in France. In this paper we present the evolution of RNF over the last thirty years, the social mechanisms of its construction, the frontiers that limit its actions. The analysis of the emergence in this network of the themes linked to the sustainable development of territories highlighted institutional, organizational, cultural and strategic issues at stake. We argue the thesis of an unfinished institutionalization symbolized by the partial substitution of the protectionist cliché by the new super-cliché of integrated conservation. We conclude by identifying the issues of changes of the network members’ composition, especially the local governance excesses’ risks related to any decentralization process and the crucial issue of inter-networks cooperation.