Throughout the two years of Brexit debates following Article 50 notification, the UK Government and Parliament consistently have failed to recognise that even if EU law is no longer applicable after Brexit, the UK is still bound to a broad gamut of rules under international law. Apparently attempting to appease Brexiteers, on 11 March Theresa May offered a unilateral statement to the EU on the UK interpretation of the Protocol on Ireland/Northern Ireland in relation to the backstop set out therein. In a similar vein, two days later, Geoffrey Cox MP argued that article 62 of the Vienna Convention on the Law of Treaties (Vienna Convention) offered an easy out of the Withdrawal Agreement and Northern Ireland backstop if a more acceptable arrangement could not be reached in the coming years. Now pundits, politicians, and academics alike are expending great energy trying to ascertain what effect the unilateral statement or article 62 may have on the Withdrawal Agreement in future. Put simply, the statement has no legal effect. Article 62 is not a panacea and both the UK government and Parliament would do well to stop relying on concepts in international law to cure all that is disagreeable with the Brexit process. International law supports the precise opposite positions asserted in both of these circumstances. If the aim in leaving the EU is to ‘be global’ without the filter of EU regulations, the application of the international rules (in which the UK had a heavy hand in drafting) must be understood as starting, rather than end, points for negotiating future relationships.

Modification of International Agreements

There are two different theories on the nature of the Withdrawal Agreement. First, it could be viewed as a bilateral treaty between the EU and the UK. Second, the Withdrawal Agreement could be understood as a multilateral treaty between the UK and the individual members of the EU. In either event, the unilateral statement has no legal value and more aptly is framed as a political manoeuvre aimed at getting Brexiteers to support the Withdrawal Agreement during the vote at Westminster last week. The statement purported to offer the UK’s interpretation of its options in the event that agreement on the Irish border cannot be reached by the deadline of 31 December 2020 (or a future extended deadline date).

The statement explains that the UK’s view is that it may unilaterally ‘instigat[e] measures that could ultimately lead to disapplication of obligations under the Protocol, in accordance with Part Six, Title III of the Withdrawal Agreement or Article 20 of the Protocol’ in the event of ‘a breach of Article 5 [good faith] of the Withdrawal Agreement by the Union’. A general reading of Article 20 of the Protocol reveals that either the EU or the UK may notify the other party that it deems parts of the Protocol no longer applicable and this would be discussed by a Joint Committee within 6 months of the notification or be referred for arbitration pursuant to Part 6, Title III of the Withdrawal Agreement. Thus, this is not exactly a statement that delivers any interpretation that necessarily falls afoul of the Agreement as it only signposts that it may ‘instigate measures’. If the UK moved to disapply any of the obligations under the Protocol in future in reliance on the statement, then this would no doubt modify the legal effect of the agreement and, therefore, the ‘interpretative declaration’ would then be subject to review as a reservation pursuant to the Vienna Convention.

The Vienna Convention defines a reservation as ‘a unilateral statement, however phrased or named, made by a State, when signing, ratifying, accepting, approving or acceding to a treaty, whereby it purports to exclude or to modify the legal effect of certain provisions of the treaty in their application to that State’ (article 2(1)(d)). The Vienna Convention embodies the customary rules of treaty law that apply to the examination of all treaties unless other rules have been expressly indicated in the agreement. In this case, no other applicable rules have been set out in the Agreement.

If the statement was intended to have any legal effect in a potential future dispute, as in change any potential obligation under the Withdrawal Agreement, the only unilateral option to alter treaty obligations following conclusion of the agreement is through a reservation. All international agreements/treaties may be subject to unilateral change after conclusion by means of a reservation, as long as the reservation is not prohibited by the agreement/treaty or does not violate the object and purpose of the agreement. The Vienna Convention rules govern whether the statement has any legal effect but we need not go much further than the definition of a reservation to make a determination on the potential of the 11 March statement to have future legal effect.

However one reads the statement (as in trying to determine what the UK is attempting to clarify) the Vienna Convention demands that to have legal effect, it must be made ‘when signing, ratifying, accepting, approving or acceding to a treaty’. The same rules would apply to an ‘interpretative declaration’ if the statement ‘purports to exclude or to modify the legal effect of certain provisions of the treaty’ because it would effectively be a reservation – the name attached to the statement is not important, it is the purported effect that triggers the application of the rules.

Pursuant to the text of the Withdrawal Agreement, it was concluded/approved on 25 November 2018 and in terms of its legal operation, it otherwise only speaks to ‘entry into force’ on 30 March 2019.  Ratification, in the strictest sense of the word, is not necessary for the Agreement to enter into force as in a traditional treaty. This is not uncommon in bilateral treaties or treaties between a small number of states. The intervening period between conclusion and entry into force has effectively given the UK time to fulfil its internal procedures, and though markedly different to those normally applicable to treaty approval under the Constitutional Reform and Governance Act 2010 (which replaced the Ponsonby Rule), this is of no importance in the consideration of the UK statement. No state may ‘invoke internal law as justification for its failure to perform a treaty’ (Vienna Convention article 27). What happens internally in the UK does not change the agreement, unless there is notification that the UK internal process did not confirm the agreement – a no deal – and then the agreement does not take effect.

As no further positive action is required for the Withdrawal Agreement to take effect, it will become a binding agreement in the absence of notification that the UK has internal disagreement and, therefore, it seems that the time in which a reservation could be made passed on 25 November 2018. Even if read as a conditional interpretative declaration, it would still need to have been made when the agreement was ‘approved’ because any purported change to the legal effect of the agreement would trigger the reservations analysis.

Fundamental Change of Circumstances

Following the second defeat of the Withdrawal Agreement in Parliament, MPs then began seeking international legal rules that would promise reprieve from a perpetual Irish backstop. Again, the constant companion of treaty lawyers was co-opted to salve certain MPs’ disdain for the idea of a permanent relationship with the EU due to the Irish border. This time, Geoffrey Cox MP invoked a rarely used treaty termination option, fundamental change of circumstances, which is codified in Vienna Convention article 62. Again, a UK politician sought to use a rule that is much more complex than it seems on the page.

At the international level, the claim of a right to terminate a treaty is just that – a claim. It is not automatic, it must be adjudicated and the International Court of Justice demonstrated in the Gabčíkovo-Nagymaros case (Hungary v Slovakia) that to be successful in claiming this right, a very high bar must be reached. Furthermore, the change must be one that was not anticipated at the time of the agreement (article 62, para 1). Thus, suggesting article 62 as a potential ‘get out’ clause for the future renders it an unavailable option because the potential perpetuation of the Irish backstop is anticipated and, therefore, runs afoul of article 62.  Not to mention that implementing a treaty while simultaneously exploring how to extricate the UK from it would breach the most fundamental rule of treaty law – pacta sunt servanda – which demands that treaties be performed in good faith (Vienna Convention article 26). Suggestions that the UK would have unilateral termination in mind even before the agreement enters into force does not suggest good faith. Entering international agreements in a post-Brexit landscape will prove more difficult if the UK gets a reputation for looking for the ‘get-out’ clause before the agreement takes effect.

It seems that despite these attempts to appease those tired of non-British regulation, the unilateral statement on the UK interpretation of the Protocol on Ireland/Northern Ireland could never have legal effect, if that is what was intended. Nor is it remotely plausible that article 62 could be successfully invoked to unilaterally terminate the Irish backstop provisions in the Withdrawal Agreement. These are simply further reminders of the UK’s failure to appreciate that regardless of EU membership there are many international rules still applicable to the UK and all sovereign nations, including those of treaty law. It also suggests that a future of unchecked, unilateral UK posturing is not the best way to promote Britain as being ‘open for business’.

Dr Kasey McCall-Smith, Lecturer in Public International Law and LLM in Human Rights, Programme Director, University of Edinburgh; Executive Chair, Association of Human Rights Institutes (AHRI).

(Suggested citation: K. McCall-Smith, ‘The Realities of Being Global: Treaty Law and Brexit’, U.K. Const. L. Blog (20th Mar. 2019) (available at https://ukconstitutionallaw.org/))