This paper examines the action of public authorities in the domain of peri-urbanization, with the aim to assess the realistic nature of planners’ ambitions for urban compactness. It is in this perspective that we analyse the intervention of public authorities by differentiating the three reference images of “planning-oriented” behaviours, “expansion-oriented” behaviours and “a spatial sector-based” behaviours. This leads to underline the multi-facet attitude of public authorities in the domain of spatial planning. This also leads to the conclusion that the concretization of compact-city objectives would require to call into question the balance between individual and collective rights as well as the conditions of local democracy and the objectives of important sector-based policies.