This article contributes to an understanding of policy change. Exploring a local land planning case, it investigates how an environmental advocacy coalition effectively challenged road and housing plans, with the result that an area was instead developed into a nature reserve. In the course of the article, the value and practical effectiveness of the Advocacy Coalition Framework (ACF) is examined and developed with the help of two central concepts—the “value network” and “inside activist”. The outcome of the case is explained by the powerful influence of a value network of ornithologists, with particular inside activists of that network playing important roles in presenting a challenge to development of the area. Instead of trying to build an abstract theory of the ACF, the article argues the need to develop the ACF as a framework, opening it up to insights from policy network and social constructionist research as well as from practical processes.