After reviewing the development of the principle of precaution at international, European and national level, the paper focuses on the relaxation of the principle of the legality-predictability of administrative measures which can occur when cautionary measures are taken in order to manage the risk of situations of uncertainty.
Compatibility with the principle of legality – considered at an internal level and in the context of the European Convention on Human Rights – of the measures adoptable by the Ministry of the Environment as per arts. 301 and 304 of the Italian environmental code in implementation of the principle of precaution is analysed from this point of view. Finally, the growing application of the principle of precaution which, in national legislation, should today be binding not only on public administration, but also on private legal entities, is critically examined.