The Role of Domestic Law in the International Legal Validity of Treaty Withdrawal

If a state withdraws from a treaty in a manner that violates its own domestic law, will this withdrawal take effect in international law? The decisions to join and withdraw from treaties are both aspects of the state’s treaty-making capacity. However, while international law provides a role for domestic legal requirements in the international validity of a state’s consent when joining a treaty, it is silent on this question in relation to treaty withdrawal. This discussion will consider this issue in light of recent controversies concerning treaty withdrawal – including the United Kingdom’s exit from the European Union, South Africa’s possible withdrawal from the International Criminal Court, and the threatened US denunciation of the Paris Agreement - and will propose that the law of treaties should be interpreted so as to develop international legal recognition for domestic rules on treaty withdrawal equivalent to that when states join treaties, such that a manifest violation of domestic law may invalidate a state’s treaty withdrawal in international law.

Hannah Woolaver is an Associate Professor in Public International Law at the Law Faculty of the University of Cape Town. Her research interests lie in public international law, focusing on the relationship between international law and domestic law, the law on the use of force, and international criminal law. Prior to joining the UCT Law Faculty in 2012, she completed her Ph.D. in international law at the University of Cambridge, B.C.L. at the University of Oxford, and LL.B. at the University of Durham. Dr. Woolaver is currently a Visiting Fellow at the Lauterpacht Centre for International Law, University of Cambridge, and the Faculty of Law, University of New South Wales, Australia, and has previously been a Visiting Scholar at the Faculty of Law, University of Toronto.