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 1 introduces the questions the book focuses on and explains its key contributions to literature on international adjudication. It introduces the three challenges facing international tribunals analysed throughout the book: managing change in applicable law or relevant facts, determining 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 explains why the book focuses on environmental disputes, as such disputes lack a dedicated tribunal and are litigated across various regimes, and how it defines such disputes. It also justifies the choice of the four adjudication contexts focused upon (adjudication in the World Trade Organization, the UN Convention on the Law of the Sea, the International Court of Justice, and under investment treaties). The chapter also notes certain insights the book incorporates from methodological debates in comparative law, given its focus on identifying and explaining similarities and differences in how the three selected challenges are managed across the four adjudication contexts studied.

Chapter 3 analyses the three selected challenges facing international tribunals – managing change, reviewing State conduct for compliance with international law, and dispute resolution – in the environmental case law of the International Tribunal for the Law of the Sea (ITLOS) and arbitral tribunals constituted under the UN Convention on the Law of the Sea (UNCLOS). UNCLOS tribunals have often interpreted the Convention in a manner that takes account of relevant developments in international law. This is partly due to features of UNCLOS itself, including that it contains many generic or open-ended terms. The chapter demonstrates that the standard and method of review are significant issues in the environmental case law of UNCLOS tribunals, in the context of the Convention conferring on coastal States discretionary powers. These issues raise similar functional questions to those seen in the other adjudication contexts studied, for example regarding the rationales for some deference to domestic authorities. Finally, the chapter demonstrates that UNCLOS tribunals often adjudicate in a facilitative, forward-looking manner, aiming to assist the parties to rebuild their relationship.

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.

This chapter argues there is a “pull” toward cross-fertilization on procedural questions, meaning cross-fertilization between international courts and tribunals may be more likely for procedural issues than in substantive law. It describes cross-fertilization in relation to procedural issues. Procedural cross-fertilization is a process and is not just about borrowing by adjudicators, but involves contributions by a range of actors. Three considerations facilitate procedural cross-fertilization and even make it somewhat likely: the discretion of adjudicators on procedural issues, adjudicators’ duty to decide numerous procedural issues, and sociological considerations concerning the circulation of a small number of personnel across multiple fora. However, two considerations counterbalance adjudicators’ broad discretion. On one hand, control mechanisms operated by states push adjudicators to remain faithful to their mandates, limiting the space for procedural cross-fertilization. On the other hand, procedural cross-fertilization feeds and is fed by an emerging model of international due process that is affecting all areas of international adjudication.