One of the most important challenges facing the international investment law regime today is how to strike a balance between principles regarding the protection and promotion of foreign investment on the one hand and principles regarding the protection of society and the environment on the other. A number of states have made significant progress towards meeting that challenge by adding interpretive provisions, general exceptions clauses and new preambular language to a new-generation of international investment agreements (IIAs). If the serious substantive and procedural questions they raise can be answered satisfactorily, these new treaties may go a long way towards saving the international investment law from the legitimacy crisis it is currently experiencing. Oxford University Press 2010, all rights reserved, Oxford University Press.