The concept of proportionality clearly refers to the ability to balance interests which are in conflict. Valentina Vada explores this issue in her chapter.

Starting from the field of constitutional law, the proportionality analysis has moved to other areas of law. The cosmopolitan character of law, after all, is well-known. In particular, it has gained a certain importance in international investment law and arbitration. The concept of proportionality clearly refers to the ability to balance interests which are in conflict. It shapes judicial review, it can restrain the exercise of public authority and manage private actors’ expectations. The aim of this chapter is considering the potential of proportionality in relation to judicial governance in international economic law in order to promote the perceived legitimacy. In her article, the author highlights that proportionality has some pitfalls if considered in economic disputes, due to the lack of consensus concerning its legal status in international law. The analysis of the issue starts with these arguments and the nit focuses on the migration of the concept in EU law. The role of proportionality is then analyzed in international investment law, arbitration and international trade law. The study includes some methodological critics regarding the identification of general principles of law. While the migration of proportionality to WTO law seems relatively settled, it is a still open issue regarding international investment law and arbitration. According to some scholars, proportionality analysis cannot be used for arbitral tribunals; they believe a degree of deference should be paid to the sovereign choices of the host state. The author, Professor Valentina Vada, considers the jurisprudence highlighting that a different perspective may be adopted in this field. In her opinion, in case international economic ‘courts’ are to use proportionality to form their interpretation of particular provisions, they should ensure that they master the relevant methodological risks and opportunities. The use of the principle of proportionality is not a neutral process: it has potentially huge consequences. What emerges in the conclusion is that more comparative constitutional law studies are needed to address the question as to whether proportionality is a general principle of international law.