Identification of Customary International Law: New Challenges and New Approaches

The Centre for International Governance and Dispute Resolution (CIGAD) at King’s College London is delighted to host a seminar on the identification of customary international law.

Customary international law is unwritten law deriving from practice and accepted as law and remains an important source of public international law. As several aspects of international law are essentially governed by customary international law alone, with few applicable treaties, the methodology for the identification of customary rules is an operation of crucial importance. In 2012 the International Law Commission took up the challenging task of producing authoritative guidance for those called upon to identify customary international law, including national and international judges, an endeavour which culminated in the adoption of the 2018 draft Conclusions on identification of customary international law.

Yet, the topic of customary international law remains ripe with challenges. For example, what is the role of individuals in general—and judges in particular—in the selection of evidence for the identification of customary international law? How can ‘change’ in customary international law be detected, and what impact does change have on the application of the two-element test for identification of custom?

The Speakers

Katie Johnston

Katie is Lecturer in Law at the University of Liverpool Law School. Katie's primary area of research is public international law, with particular interests in the law on the use of force (jus ad bellum) and the sources of international law. In addition to general international law, Katie’s research interests include international human rights law; international organisations law; and UK and Northern Ireland public and constitutional law, in particular the status of the Good Friday Agreement. Originally from Northern Ireland, Katie completed her D.Phil. (PhD) in Law at the University of Oxford. She also holds a M.A. in Law with Law Studies in Europe and M.Phil. from the University of Oxford and a degree from the Université Paris II Panthéon-Assas. She completed her LL.M. at Georgetown Law in Washington, D.C., where she was a UK-US Fulbright Scholar. Katie has previously worked for the UK Law Commission; in the legal department of an international organisation; and for a human rights NGO in Phnom Penh, Cambodia.

Massimo Lando

Massimo is Assistant Professor at the Law School of City University of Hong Kong. In September 2023, he will join the Faculty of Law of the University of Hong Kong. He was Associate Legal Officer at the International Court of Justice in 2017-2020 and was conferred a PhD by the University of Cambridge in 2019. He is a member of the Bar of England and Wales. In 2025, he will be Director of Studies at the Winter Session of The Hague Academy of International Law.

Sir Michael Wood

Sir Michael has been a member of the United Nations (UN) International Law Commission from 2008 to 2022 and Special Rapporteur on the topic of identification of customary international law. He was the principal Legal Adviser to the Foreign and Commonwealth Office (FCO) between 1999 and 2006. During his 35 years as an FCO lawyer, Michael attended many international conferences, including the UN Conference on the Law of the Sea. He spent three years at the UK Mission to the UN in New York, dealing chiefly with Security Council matters. Since leaving the FCO in 2006, Sir Michael has acted for many governments in cases before the International Court of Justice (ICJ), European Court of Human Rights (ECHR), International Tribunal for the Law of the Sea and inter-state arbitral tribunals. He has written extensively on public international law.