The Agences de l’eau (Water Agencies) are well known abroad as the French attempt to develop integrated water management at river basin scale through the implementation of the Polluter Pays Principle (PPP). Yet, after 30 years of existence, environmental economists became aware that they were not implementing the PPP, and therefore were not aiming at reducing pollution through economic efficiency. Behind the purported success story, which still attracts visitors from abroad, a crisis has been recently growing. Initially based on the model of the German (rather than Dutch) waterboards, the French system always remained fragile and quasi-unconstitutional. It failed to choose between two legal, economic and institutional conceptions of river basin management. These principles differ on the definition of the PPP, and on the role of levies paid by water users. After presenting these two contrasting visions, the paper revisits the history of the French Agences, to show that, unwilling to modify the Constitution to make room for specific institutions to manage common pool resources, Parliament and administrative elites brought the system to levels of complexity and incoherence which might doom the experiment.