ABSTRACT
This chapter outlines the conditions under which any extraneous norm could provide a viable defence for respondents in investment arbitration in a principled and internally coherent way. Grounded on research in private international law and legal theory, on occasion completed by comparative public law, it presents the practically relevant insights of these sources. The chapter defines the questions relevant for the integration of extraneous norms in investment arbitration. On this basis, it then offers a conceptual framework for the place of extraneous norms in investment arbitration. In order to explain the relation between investment tribunals and states acting jointly at the international level, it is practical to refer to two revealing statements. The first comes out of the United States pleadings in Glamis Gold. The second statement is authored by Jan Paulsson in a, by now, classic paper and is relevant for understanding the role of investment tribunals.
