Chapter 5 analyses the three challenges facing international tribunals considered in this book in investment treaty arbitration. Regarding the challenge of managing change, investment treaty arbitration displays similarities and differences with the inter-State tribunals studied. Using the example of the minimum standard of treatment, the chapter shows that like the inter-State tribunals studied, investment treaty tribunals contribute to broader processes of change in international legal norms. Yet differently from the other tribunals studied, investment treaty arbitration has an overriding focus on determining the permissible degree of change in host State regulation. In relation to scrutinising State conduct for compliance with international law, investment treaty arbitration raises comparable questions to the other international tribunals studied regarding the appropriate intensity of review and the methods of review used by adjudicators. Finally, the chapter considers why, unlike the inter-State tribunals studied, investment treaty tribunals rarely adjudicate in a facilitative, forward-looking manner that aims to complement post-adjudication cooperation between the parties.

Chapter 4 analyses the three selected challenges facing international tribunals – managing change, reviewing State conduct for compliance with international law, and dispute resolution – in the International Court of Justice (ICJ)’s environmental case law. The ICJ has repeatedly adapted aging treaty frameworks given relevant developments in international law and has also faced the problem of change in relevant facts. While the terminology of a standard of review is not firmly established in the ICJ’s case law, the underlying functional problem – concerning the intensity of an international tribunal’s scrutiny of determinations made by domestic authorities – is clearly present. Although three-step proportionality analysis is not entrenched in the ICJ’s case law, the Court has repeatedly used a reasonableness-based test that operates similarly to least restrictive means testing. Finally, the ICJ often adjudicates in a forward-looking, facilitative manner, seeking to assist the parties to manage their relationship after adjudication. Throughout, the chapter reflects on how the ICJ’s practices are shaped by its institutional features, such as its lack of any compulsory jurisdiction.

Chapter 6 draws together and extends the comparative analysis that has unfolded across the prior chapters. It explains why tribunals’ practices differ across the regimes studied, focusing on contextual differences between the selected tribunals. It also assesses to what extent the practices of the selected tribunals provide insights into wider problems facing international adjudication and legal techniques that are potentially transferable across contexts. Structurally, the chapter discusses consecutively my findings in relation to the three challenges confronting international tribunals analysed throughout the book: managing changes in international law or relevant facts, calibrating the appropriate standard and method of review when scrutinising State conduct for compliance with international law, and contributing to broader processes of dispute resolution. The chapter finishes with some final remarks that close the book, concerning its contribution to our understanding of the role of international adjudication in contemporary international law and its implications for future studies in this field.

Chapter 2 analyses the three selected challenges facing international tribunals – managing change, reviewing State conduct for compliance with international law, and dispute resolution – in World Trade Organization (WTO) adjudication, focusing on environmental disputes. WTO tribunals have often been faced with potential changes in international legal norms or changes in relevant facts. The chapter analyses the approach to the standard of review developed under the Agreement on the Application of Sanitary and Phytosanitary Measures. While this approach avoids WTO adjudicators determining questions of scientific correctness, it requires them to decide what counts as an adequate risk assessment process. The chapter then analyses the necessity tests developed by WTO adjudicators for scrutinising measures that pursue a permissible regulatory aim but also restrict a treaty-protected interest in trade liberalisation. Finally, the chapter interrogates an aspect of the WTO’s ‘chapeau jurisprudence’ that many commentators have read as a desirable example of international tribunals engaging in a procedural form of scrutiny and pushing regulating States to consider affected foreign interests.

For a restriction of a Convention right to be justified, it is not enough for it to have a sound legal basis and to pursue a legitimate aim. Restrictions of derogable Convention rights also must be shown to be ’necessary in a democratic society’ or ’proportionate’. Over time the Court itself has also defined a variety of specific tests and formulas to give shape to the tests of necessity and proportionality, which are all addressed in this chapter. The general test of necessity is explored first, paying special attention to the related pressing social need test, the ’relevant and sufficient’test and the least intrusive means test. Furthermore, the chapter discusses the fair balance test (a variant of proportionality in the strict sence) and some related tests, such as the individual and excessive burden test and core rights review. Attention is also paid to the related question of whether balancing should always be conducted on an individual and concrete basis on the national level, or whether blanket rules may sometimes suffice. Lastly, it is explored how procedural review can complement the Court’s substantive reasonableness review of restrictions.