Mutual Defence Agreement and the Nuclear Non-Proliferation Treaty

JOINT ADVICE

Introduction and Summary of Advice

1. We are asked to advise BASIC (the British American Security Information Council), the Acronym Institute for Disarmament Diplomacy and Peacerights. The question on which our advice is sought is whether the UK is in breach of the Nuclear Non-Proliferation Treaty (NPT) by its renewal of the Mutual Defence Agreement (MDA) with the USA. This raises a number of interlocking questions of treaty law including the relationship between the two treaties; interpretation of their terms; the status of the documents of the Review Conferences; and the meaning of breach of international obligations.
   
   
2. In our view, for the reasons set out below, it is strongly arguable that the renewal of the Mutual Defence Agreement is in breach of the nuclear Non-Proliferation Treaty.

Applicable Treaty Law

1. The principles relating to the law of treaties are largely codified in the Vienna Convention on the Law of Treaties, 1969, 1155 UNTS (VCLT). The United Kingdom is a party to the VCLT (ratified 25 June 1971), which came into force 27 January 1980. The VCLT does not have retroactive effect (article 4) and therefore does not apply to the original MDA, 1958, although it does so with respect to renewals subsequent to the coming into force of the VCLT. The VCLT does not apply to the NPT, which came into force on 5 March 1970.
   
   
2. However some provisions of the VCLT have been explicitly accepted as constituting customary international law, including those on material breach and interpretation. (E.g. Legal Consequences for States of the Continued Presence of South Africa in Namibia (South West Africa) Notwithstanding Security Council 276 (1970) 1971 ICJ Rep. 16, 47; Fisheries Jurisdiction Case (United Kingdom v. Iceland) 1974 ICJ Rep. 3, para. 36). Whether the provisions on successive treaties constitute customary international law has not been explicitly addressed, for example by the International Court of Justice but it is widely accepted that the Convention 'constitutes the basic framework for any discussion of the nature and characteristics of treaties.' (Shaw, International Law, 5th ed. 2003, 811). Brownlie states that 'certainly those provisions which are not [declaratory of existing law] constitute presumptive evidence of emergent rules of general international law.' (Brownlie, General Principles of International Law, 5th ed. 1998, 608). The United States is not a party to the VCLT but does accept the position that it restates much existing law.

Successive Treaties

1. It is first necessary to determine the temporal relationship between two possibly inconsistent treaties. The MDA was agreed in 1958, prior to the NPT, which was adopted by the General Assembly (GA), on 12 June 1968 and came into force on 5 March 1970. However the MDA has been subject to renewal, most recently in 1994. Renewal of the MDA constitutes a new treaty for the purposes of domestic law procedures for its adoption. (Senior Research Clerk, International Affairs and Defence Section, House of Commons Library: 'The Amendment was a treaty itself, and hence it was subject to normal treaty law and practices.' (Bundle, Tab 1, p. 8). It is accordingly also to be regarded as a new treaty for the purposes of international law.
   
   
2. The NPT was indefinitely and unconditionally extended by the Review and Extension Conference on 11 May 1995. This was not a renewal of the Treaty (thereby implying a new Treaty) but rather an extension of the existing Treaty in accordance with its own terms: Article X (2).
   
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