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New Book by Daniel Peat - Comparative Reasoning in International Courts and Tribunals

Cambridge Studies in International and Comparative Law

About the book

The interaction between domestic law and international law is a topic of perennial interest for international lawyers. Domestic law has long been recognised as a source of international law, an inspiration for legal developments, or the benchmark against which a legal system is to be assessed. Often, it is simply treated as mere fact, indicative of the legality of a state’s actions. Academic commentary normally re-traces these well-trodden paths, leaving one with the impression that the interaction between domestic and international law has been thoroughly mapped, and is unworthy of further enquiry. However, a different – and surprisingly pervasive – nexus between the two spheres has been largely overlooked: the use of domestic law in the interpretation of international law.

A new book by Assistant Professor Daniel Peat, Comparative Reasoning in International Courts and Tribunals (Cambridge University Press 2019), aims to fill that gap in the literature. It examines the practice of five international courts and tribunals in order to demonstrate that domestic law is frequently invoked to interpret international law, often outside the framework of Articles 31 to 33 of the Vienna Convention on the Law of Treaties. The book assesses the appropriateness of such recourse to domestic law in its legal and historical context, as well as situating the practice within broader debates regarding interpretation and the interaction between domestic and international legal systems.

Before joining Leiden University, Daniel worked at the International Court of Justice as an Associate Legal Officer for President Abdulqawi A. Yusuf from 2015 to 2018. He was awarded a PhD in Law from the University of Cambridge, where he was a member of Gonville & Caius College and a recipient of the WM Tapp Studentship. Daniel is co-editor of Interpretation in International Law, published by Oxford University Press in 2015. He continues to conduct research on treaty interpretation in his capacity as Rapporteur for the ILA Study Group on the Content and Evolution of the Rules of Interpretation. At Leiden, Daniel teaches primarily on the LLM Adv. in International Dispute Settlement and Arbitration.

Advance reviews of the book

‘Dr Peat has offered fresh insights into two under-studied topics - the place of domestic law in treaty interpretation and the comparative jurisprudence of international courts and tribunals. By calling attention to commonalities and distinctions among the approaches of various courts and identifying judicial practices that may not fit neatly into orthodox narratives, the volume promises to be valuable to scholars, practitioners and jurists alike.’
Joan Donoghue - Judge of the International Court of Justice, Netherlands 

‘A very clear and revealing account of the use of domestic law by international courts and tribunals when interpreting international instruments and international law. This sheds helpful light on important matters of current legal interest.’
Richard Gardiner - University College London 

‘Tribute must be paid to Daniel Peat for his masterful dissertation, offering a brilliant analysis of the complex issue of the interaction between domestic and international law in international dispute settlement. It explores the profound implications of this normative interaction, shifting the perspective to the comparative reasoning of international adjudicators. The analysis of different jurisdictional settings, the diachronic approach and the sharp reading of the case law make this book a fascinating piece of scholarship.’
Hélène Ruiz Fabri - Director, Max Planck Institute Luxembourg for Procedural Law

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