The implementation of the sustainable development principle of integration implies that economic laws should not be designed solely for the purpose of maximizing financial profits, but also with the object of improving human well-being, and addressing social and environmental concerns. International organizations, in which international treaties are being negotiated and created, will have to support this type of cross-disciplinary approach. International institutions, however, were not originally designed to cope with such a cross-disciplinary effort. Rather, most international institutions have emerged in line with the premise of ‘functionalism’, according to which their role is limited to supplying specialized services, usually as a solution for emerging needs and as a result of historical events. These specialized institutions have thus emerged with little coordination or common planning and have resulted in a global structure that has been referred to as an ‘accident of history’. The role that international organizations should and do fulfill with respect to the implementation of the principle of integration is reviewed in this paper. This paper concentrates on trade and investment organizations (the World Trade Organization and the Energy Charter Treaty); it reviews the channels through which non-trade/investment considerations may, or may not, penetrate the decision-making processes of these organizations; the ways these International organizations engage with interdisciplinary issues and how the objectives of other institutions are reflected in their work