Legal personhood has been recognized for several ecosystems worldwide, garnering significant attention from the scholarly community. This attention translated with the mobilization of approaches anchored into legal, institutional, or ethnographic perspectives. On-going calls for the recognition of Rhone River’s legal personhood provides us the opportunity to analyze on-going processes in a transboundary river located in the middle of Europe. This paper focuses on how such a concept gets promoted and intends to make its way on the political agenda. Specifically, we examine two current promoters of the legal personhood of the Rhone River: the International Commission for the Protection of Lake Geneva (CIPEL) and ID-Eau. We identify five key lessons: (1) the request for recognition of legal personhood derives from actors’ willingness to change current governance practices and to shift the productivist paradigm towards more decentralized and inclusive governance system; (2) legal personhood is presented as a solution to problems that have not yet been clearly framed nor identified, opening up thinking on how such concept may be instrumentalized; (3) the discussion remains limited to a small number of experts; (4) the legitimacy of this debate requires scrutiny; (5) the legal personhood concept should be reinterpreted to fit within Western ontologies.