An international team of authors set down their thoughts on the European Commission's 'Precautionary principle' in the latest issue of the journal 'Science'. The precautionary principle, adopted earlier this year after lengthy discussions, now forms the backbone of environmental law in the European Union. In its simplest terms, it encourages Member States to err on the side of caution when regulating new technologies. Yet, the precautionary principle is surrounded by controversy. Before its adoption there was opposition based on concerns that it would set up unfair trade barriers. Now its critics say governments have applied the principle arbitrarily. In the paper published in 'Science', researchers discuss recent guidelines from the European Commission intended to clarify how the principle should be used when considering new technologies. 'The guidelines emphasise the need for a politically transparent process and a careful review of scientific data when using the principle, which 'may help reduce the contentiousness of its application,'' say the authors.