Le principe de précaution comme norme de l'action publique, ou la proportionnalité en question

In France the precautionary principle gave birth to two basic opposite interpretations. The first one, fixed in the French legal framework and developed by the European doctrine, supports an early but proportionate consideration of potential hazards. The second one has been backed by environmental ngo s and disseminated into current use by media and political circles under crisis circumstances. It asks for a proof of no-risk and aims at eradicating all sources of hazards to the possible extent. As a result, a basic confusion arose between two ideas : to take early preventive action, and to accumulate more stringent preventive measures. Firstly, the paper sketches the landscape of competing concepts. It then shows why the « abstention rule » cannot be supported, even when its requirements are attenuated. It also identifies how a wrong framing of the decision problem leads a specific artefact to arise, by which earliness in the scientific time induces an overall inflation of risks through a perception of increased potential damage. To keep the precautionary principle on the right track, two requirements are to be met : enforcing the consideration of potential benefits the same way as potential hazards ; proportioning preventive measures to the scientific plausibility of hypotheses of risks, in order to give a lower weight to assumptions deprived of significant evidence. Classification JEL : A13, D81, I18, K32.