The Globalization, Law & Justice Workshop sponsors occasional events.

Globalization, Law & Justice Series


Dr. Hannah Woolaver
University of Capetown

From Joining to Leaving: Domestic Law’s Role in the International Legal Validity of Treaty Withdrawal

Tuesday, December 5, 2017
12:30 - 1:45
Flavelle House, Room 223 (Betty Ho Classroom)
78 Queen's Park

The boundaries between international and domestic systems of public law are complex and dynamic. As the scope and ambition of public international law expands, this has significant implications for the conception of state sovereignty in international law, and also for domestic public law. These challenges can become acute especially in the realm of constitutional law. This paper will address the relationship between international and domestic public law in the context of states’ exit from international treaties. In particular, it will examine the role of domestic constitutional rules in the international legality of states’ withdrawal from treaties.  

The question whether the manner of a state’s withdrawal from a treaty must comply with its domestic constitutional rules to have effect in international law is of widespread and topical importance. It has recently arisen, inter alia, in relation to the UK’s exit from the European Union, South Africa’s possible departure from the International Criminal Court, and the threatened renunciation of various treaty regimes by the USA. Surprisingly, the topic has not yet received significant judicial or scholarly attention.  Further, the Vienna Convention on the Law of Treaties 1969 (VCLT), the leading instrument on the law of treaties, is silent on the question. While the VCLT provides that a violation of the state’s internal law can vitiate a state’s consent when joining a treaty - a rule which has generated much judicial, diplomatic, and scholarly comment - there is no equivalent provision relating to treaty exit. Furthermore, relevant national case law addressing constitutional requirements for treaty withdrawal does so purely from the perspective of domestic public law, without addressing whether an unconstitutional withdrawal may nonetheless be effective in international law. 

The paper will proceed in four parts. First, an outline of the relationship between international and domestic public law in the law of treaties will be provided, setting out the tension between two competing imperatives in international law: the certainty and security of treaty regimes, and respect for state sovereignty and domestic constitutional rules. Second, the varying domestic public law approaches to treaty withdrawal will be examined, including consideration of the recent case studies involving the UK, South Africa, and the USA noted above. Third, it will be explored whether, despite the absence of treaty-based regulation, the international lex lata integrates recognition of the requirements of domestic public law when assessing the legality of a state’s treaty withdrawal. Finally, it will be proposed that, de lege ferenda, while generally violation of domestic public law should not invalidate a state’s treaty withdrawal for the purposes of international law, an exception should be recognized: if the manner of withdrawal constituted a manifest violation of a domestic public law rule of fundamental importance, then it should be ineffective in international law. Such a development would balance the imperatives of treaty security and the fundamental right of states to sovereign equality, bring the rules of joining and exiting treaties into parallel, and represent a positive clarification of the frontier between domestic and international public law.

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