Defence date: 11 June 2005 Examining board: Prof. Giafnranco Poggi (supervisor, European University Institute, Florence) ; Prof. Simone Bateman (University of Paris V) ; Prof. John Griffiths (University of Groningen) ; Prof. Martin Kohli (European University Institute, Florence) PDF of thesis uploaded from the Library digitised archive of EUI PhD theses completed between 2013 and 2017 This thesis is a case study of social engineering investigating how, in France, a legislative effort formally aimed at modifying organ donation behaviour was atempted, and why it failed. The law studied was voted in 1976, and established a presumption of consent to cadaveric organ donation. This research focuses on data derived from the site in which the practices this law is supposed to regulate take place: interviews with nurses and physicians in charge of decisions about organ retrieval, a survey, and regular informal contacts with them. To contextualize this information, a historical analysis of parliamentary reports, discussions, and law drafts between 1975 and 2004 has been conducted; and public discourse produced by the written press between 1992 and 2004 analysed. Following the law from Parliament to hospitals, from its formal elaboration to its confrontation in practice with a plurality of non-legal norms, this thesis shows that professionals holding the formal power of presuming the consent of potential donors only occasionally resorted to it before the late 1980s, and ceased doing so in the 1990s. Currently, the presumption of consent is not applied when it contrasts with the view of relatives' of potential donors. What accounts for this are, according to professionals, a general context where French political and health institutions have lost part of their legitimacy to impose behaviour upon the general population; claims for autonomy of patients and families; the characteristics of the situation where decisions of retrieval occur, where sudden deaths are announced; the insufficiency of measures that at the level of policy have accompanied a law based on the principle nemo censetur ignorare legem. Confronting legislative and policy action and what occurs in practice, it seems that law and policy-makers had, initially, counted on the issuing of a law alone to see behaviour change; subsequently, they appear to feel impotent before the general population.