Preserving biological biodiversity on the continent scale, such is the challenge that the European Union intends to take up by adopting the 1992 Habitats directive. Through this initiative, European decision-makers wish to bring their contribution to what is now one of the planet’s new stakes. The research results presented here give an account of the implementation of this policy at the French national level. They focus on the elaboration phase (1999-2005) of “documents of objective”, during which a management plan had to be produced for each site designated by the Directive, targeting biodiversity conservation objectives. The analysis examines the concerted elaboration process of management actions at the site level, in particular questioning the interactive dynamics between the protagonists mobilised.