This book explores how the Permanent Court of International Justice, the International Court of Justice, the European Court of Human Rights, and investment treaty tribunals have used deference to recognise the decision making authority of States. It analyses the approaches to deference taken by these four international courts and tribunals in 1,714 decisions produced between 1924 and 2019 concerning alleged State interferences with private property. The book identifies a large number of techniques capable of achieving deference to domestic decision-making in international adjudication. It groups these techniques to identify seven distinct 'modes' of deference reflecting differently structured relationships between international adjudicators and domestic decision-makers. These differing approaches to deference are shown to hold systemic significance. They reveal the shifting nature and structure of adjudication under international law and its relationship to domestic decision making authority.

Hounorable mention 2022 Australian Legal Research Book Award, Australian Legal Research Awards

'International judges and arbitrators, as well as parties appearing before them, use various monikers to call for some degree of deference to national decision-makers. Dr Shirlow's ground-breaking study of multiple dispute settlement mechanisms combines empirical, inductive and comparative inquiries to shine light on the diverse ways in which deference operates in international courts and tribunals, deepening our appreciation of particular institutions and providing rich comparisons among institutions and over time.'

Judge Joan Donoghue - International Court of Justice

'Deference is one of those rare concepts that are as pervasive as they are difficult to chart, not only conceptually or phenomenologically, but legally. Dr Shirlow has cracked this intractable equation with impressive analytical distance and great pragmatism. Her study is an important contribution from both a theoretical and a practical perspective.'

Jorge. E. Viñuales - Professor of Law and Environmental Policy, University of Cambridge

'Judging at the Interface is a sophisticated and comprehensive analysis of when international adjudication defers to State decision-making. Drawing on the treatment of private property disputes by different international bodies and on a vast range of empirical evidence, Dr Shirlow establishes a framework that identifies the various ways in which such deference is manifested. As Dr Shirlow concludes, this interface is not just about competing theoretical approaches, but also about broader concepts of authority over disputes, the legitimate role of domestic and international systems in their resolution, and ultimately the relationship between law and politics.'

Meg Kinnear - Vice President and ICSID Secretary-General, International Centre for Settlement of Investment Disputes

'Deference has become a central battleground in international adjudication. Starting from the link between sovereignty and deference, Dr Shirlow's exceptionally rich study provides fresh thinking on deference's functions and evolution, and comprehensive empirical evidence on deference as an adjudicative practice. Dr Shirlow's tour de force will be the first port of call for anyone concerned with deference in international adjudication. Her book is also a delight to read - highly recommended!'

Michael Waibel - Professor of International Law, University of Vienna