The issue of the use of genetic engineering in crops and food production is not only a scientifical one. It is a social debate. The multinational companies of agrobiotechnology have interests that are opposed to the environmental concerns of many countries and NGOs. Of course modern biotechnology of DNA recombination can increase agricultural productivity but concerns have arisen about its potential adverse effects on biological diversity and human health. This paper deals with some of the social issues at stake by the use of GMOs in agriculture and food. It relates the recent emergence of the precautionary principle in international trade of GMOs. The adoption of the precautionary principle in the Protocol on Biosafety has created a normative framework in international commerce of GMOs but also in the social debate.