Résumé
Originally conceived as a technique of territorial organization of the unitary State, the process of decentralization produces effects on the whole of the unitary legal system. It is a concept that "embarrasses" jurists because first of all on the form since the methodology of analysis induces to make a "state of the art" with disciplines other than law to understand territorial decentralization (public management, economics, political science , geography, history, etc.). In terms of substance, the hypothesis was then to start from a tripartite dimension of decentralization (object, function, subject). This approach makes it possible to account for the evolution of relations between the State and local authorities in Europe based on two examples of a unitary State adopting a similar conception in the original mechanisms of decentralization but adapted to the political and historical context of the two States. This is how the unitary state develops the unitary law of the state and thus redistributes the competences and powers of each entity. First, at the internal level with a renewal of the classic conception of the unitary State which makes it possible to envisage both legal and political pluralism. The local authorities play an undeniable counter-power role when the central power tries to return to a more or less "extremist" form of supervision. Then on the external level, a repositioning of the "classic" unitary State is perceptible by local public action since the local authorities themselves adapt their functioning with regard to external constraints by adopting private and public cooperation tools.