UK Constitutional Law Association

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Jake Rylatt: The Irrevocability of an Article 50 Notification: Lex Specialis and the Irrelevance of the Purported Customary Right to Unilaterally Revoke

RylattWith the constitution of a new UK Government formed around a policy of ‘Brexit’, and the creation of the new ministerial position of ‘Secretary of State for Exiting the European Union’, the likelihood that Article 50 will actually be triggered has increased significantly. In addition to the cavalcade of recent posts addressing who is constitutionally empowered to make the Article 50 notification, attention has also been given to the question of whether an Article 50 notification made in conformity with the constitutional requirements of the UK could be subsequently revoked. An interesting argument raised by Charles Streeten is that ‘an Article 50 notification can be withdrawn unilaterally at any point prior to the expiry of the two year guillotine imposed by Article 50’. This post responds by challenging this argument on two grounds, arguing that ultimately a Member State cannot unilaterally revoke an Article 50 notification once it is made. It will do so by firstly outlining the argument made by Streeten, before explaining its difficulties and attempting to clarify the legal position. In concluding, it will be argued that the decision to trigger Article 50 is one that should be taken with the greatest care; relying upon technical legal arguments to provide a safety net risks creating further uncertainty and undermining the position of the UK in subsequent negotiations.

Streeten on Article 50

The argument of Streeten is constructed as follows:

(1) Whether or not Article 50 contains an implicit power to revoke a notification is a matter of EU (as apposed to Public International) law.

(2) It has been held by the CJEU that in so far as the Vienna Convention on the Law of Treaties (‘VCLT’) reflects customary international law it is binding on the EU.

(3) Article 68 VCLT provides that ‘a notification or instrument provided for in article 65 or 67 may be revoked at any time before it takes effect’. ‘Takes effect’, in turn, is interpreted by Streeten as meaning ‘the termination of a treaty or the withdrawal of a party’, not simply providing the relevant notification of intent to withdraw.

(4) Article 68 VCLT represents customary international law.

(5) The right reflected in Article 68 VCLT ‘is implicit absent explicit provision to the contrary and the CJEU is bound to interpret the two year notification period specified in Article 50 as importing such a right’.

In sum, the argument is that Article 68 VCLT, as a manifestation of customary international law, operates to fill the gaps in the Article 50 withdrawal provisions. There is no doubt that this is a carefully constructed argument. However, and placing to one side the potential minor stumbling block that is step (3) (the interpretation of ‘takes effect’ in Article 68), the primary difficulties in this argument are steps (4) and (5).

The Customary Status of Article 68 VCLT

First, there are serious doubts as to whether Article 68 VCLT represents a rule of customary international law. Even accepting that its adoption without a dissenting vote is indicative of customary status, an argument not entirely clear on a close reading of the Namibia Advisory Opinion, this alone is not determinative of its customary status.

In determining the status of Article 68, two periods of time are important: the period prior to the VCLT being agreed; and the period since the VCLT was agreed. With regards to the first period, Tzanakopoulos, commenting on Article 67, notes that:

“The ILC, Special Rapporteur Waldock, State delegations at the Vienna Conference, and most commentators, seem unequivocally to agree that the Articles on procedure did not codify pre-existing law, but rather constituted progressive development at the time, introducing an innovation in the law of treaties.” Tzanakopoulos, ‘Article 67’ in VCLT Commentary (OUP, 2011), p. 1548 [references omitted].

As such, it was clear that the VCLT articles on procedure, including Article 68, were a progressive development as opposed to a codification of pre-existing customary international law.

With regards to the second period, and in considering whether Article 68 has subsequently crystallised into custom, Tzanakopoulos argues that:

“…[T]he right to revoke a unilateral act before it has taken effect is considered by the ILC as being implicit when there is a gap in time between the promulgation of the act and the production of legal effect. As such, any customary character of Article 68 would be intimately connected with the customary character of Articles 65(1) with respect to notification and 67(2) with respect to the instrument executing the notified measure. In this connection it should be noted that the notification of Article 65(1) seems to indeed reflect customary law, if not in all its particular details (ie that it must be in writing, as provided for in Art. 67(1)). However, the provision of Article 67(2) cannot probably be considered customary law, and as such neither can the relevant part of Article 68.” Tzanakopoulos, ‘Article 68’ in VCLT Commentary (OUP, 2011), p. 1565 [references omitted].

Consequently, the argument follows that the customary status of Article 68, or at least the part relevant for present purposes, is parasitic on the customary status of Article 65(1). No attempt is made to ground the customary status of Article 68 in state practice and opinio juris relating specifically to that provision. Furthermore, even accepting that the prima facie simplicity of Article 68 can be subdivided into multiple rules, each with their own status vis-à-vis customary international law, there is little support for the proposition that even Article 65 reflects custom. While it has been argued that the International Court of Justice (‘ICJ’) in Gabčíkovo-Nagymaros ‘endorsed’ the argument that the core of Article 65 reflects custom (Prost, ‘Article 65’ in VCLT Commentary (OUP, 2011), p. 1488), this misrepresents the situation. Instead, the Court simply noted the agreement of the parties:

“[T]hat Articles 65 to 67 of the Vienna Convention on the Law of Treaties, if not codifying customary law, at least generally reflect customary international law and contain certain procedural principles which are based on an obligation to act in good faith.” Gabčíkovo-Nagymaros Project (Hungary/Slovakia), Judgment, ICJ Reports 1997, para 109.

As such, there are serious doubts as to the customary nature of Article 68. As a brief aside, it is noted that even if the CJEU was to rely on an EU equivalent of the principle of ‘good faith’, as it has previously [Case C-203/07 P Greece v Commission [2008] ECR I-8161, para 64; Case T-115/94 Opel Austria v Council [1997] ECR II-39, paras 90-1], the parties before the ICJ in Gabčíkovo limited their understanding of that principle as encompassing only Article 65 to 67 VCLT, not Article 68. There is nothing to suggest a different position would be taken by the CJEU.

Article 68 as custom: Lex Specialis and the comprehensiveness of the Article 50 regime

In the instance that Article 68 is considered by the CJEU to be custom, a question arises as to how Article 50 TEU and the customary right to unilaterally revoke a withdrawal notice interact. Two possibilities arise:

  • The unilateral right to revoke is inserted into the machinery of Article 50; or
  • Article 50 operates to displace the customary regime via the principle of lex specialis derogat lex generali, and therefore the unilateral right to revoke is inapplicable.

It is submitted that the second option reflects the stronger legal position. With regards to the first option, essentially capturing the argument of Streeten, there is an assumption made that the right to revoke can be separated from the rest of the procedural regime on withdrawal. However, as noted by Tzanakopoulos:

“Together, all four procedural Articles and the Annex to the Convention have the purpose of establishing a ‘regular procedure’ for declaring the invalidity or effecting the termination or suspension of a treaty.” – Tzanakopoulos, ‘Article 67’ in VCLT Commentary (OUP, 2011), p. 1546.

The difficulty that emerges in the argument of Streeten, then, is that it purports to cherry-pick one element of this ‘regular procedure’ and place it within a specific procedure established by Article 50 TEU. It is submitted that this difficulty is not undermined by (at least part of) the rule originally enunciated in Article 68 assuming the status of custom. Even if only some elements of the Article 65-68 VCLT procedure were found to be customary, it is unlikely that the CJEU would consider those elements to be severable based on the original intentions of the treaty regime from which the customary rules emerged. While it is well established that treaty and custom on the same issue can exist simultaneously [Military and Paramilitary Activities in and against Nicaragua (Nicaragua/USA), Jurisdiction and Admissibility, Judgment, ICJ Reports 1986, para 73], and even have diverging contents, there is little, if any, state practice or opinio juris to suggest this has happened in this case.

Furthermore, it is submitted that while Article 50 TEU is indeed silent on the question of whether an Article 50 notification is revocable, this does not necessarily make the regime susceptible to incorporating elements of customary international law. In fact, the wording of Article 50(3) militates against this interpretation of Article 50. Specifically, Article 50(3) provides that:

“3. The Treaties shall cease to apply to the State in question from the date of entry into force of the withdrawal agreement or, failing that, two years after the notification referred to in paragraph 2, unless the European Council, in agreement with the Member State concerned, unanimously decides to extend this period.”

As such, Article 50(3) explicitly addresses the ultimate result of an Article 50 notification, the cessation of the EU constitutive treaties, and recognises only a single instance where this can be possibly delayed, namely in the case of agreement between the European Council, acting unanimously, and the Member State making the notification. The argument therefore follows that there is no gap in Article 50 into which a customary unilateral right to revoke a withdrawal notification may slot, since Article 50 expressly addresses possible limits on the cessation of the EU treaties.

Consequently, the interaction between the customary regime of treaty withdrawal and the treaty-based procedure in Article 50 TEU is better viewed as a conflict of norms between two complete bodies of norms. In reconciling these two bodies of norms, the principle of lex specialis derogat lex generali (the specific law takes precedence over the general law) applies. The rules in the VCLT and custom on procedure are inherently residual, a lex generalis applying in situations where a treaty is silent on the issue of withdrawal or denunciation. Where a treaty makes provision for these issues, as Article 50 TEU does in this case, those rules provide the lex specialis.

It is unsatisfactory to simply say that the lex specalis principle in all cases requires a wholesale displacement of the general in favour of the specific; the 2006 International Law Commission ‘Conclusions of the work of the Study Group on the Fragmentation of International Law’ reflect the multiple ways in which a lex generalis may retain a role within a lex specialis. However, in the present circumstances, where two complete regimes clash, Article 50 applies to the complete exclusion of the customary rules on treaty withdrawal procedure. Consequently, Article 50 TEU prevails in the terms in which it is couched, with no room to imply a right to revoke a withdrawal notification from custom.

Finally, it is to be noted that this approach more closely reflects the manner in which the CJEU has generally viewed customary international law. Specifically, it may be observed that the CJEU has, in practice though not explicitly, drawn a distinction between issues on which the EU constitutive treaties are silent, and those issues for which the treaties make some provision; only in the former case has the Court been accommodating of customary rules. For example, despite the presence of a customary right to undertake countermeasures in certain circumstances, one jurisprudence constante of the CJEU has refused to allow Member States to take countermeasures outside the EU enforcement procedures [Case 26/62 Van Gen den Loos [1963] ECR 1, p.12; Joined Cases 90/63 and 91/63 Commission v Luxemburg and Belgium ECR [1964] 625; Case 6/64 Costa v ENEL [1964] ECR 585, 593]. In contrast, the Court has consistently had recourse to customary principles of treaty interpretation [Case C-410/11 Sánchez et al. v Iberia Líneas Aéreas de España SA, paras 21-2; Case C-268/99 Jany and others v Staatssecretaris van Justitie, para 35], a matter on which the treaties are silent. In the instance case, where Article 50 TEU expressly addresses the issue of withdrawal from the EU, it seems unlikely that the CJEU would depart from this approach and undermine its recent attempts to reassert the autonomy of the EU legal order [Joined Cases C-402/05 P and C-415/05 P Kadi and Al Barakaat v Council and Commission [2008] ECR 2008 I-06351, para 282].


The above analysis reflects that there are two major difficulties in incorporating into Article 50 TEU the right to unilaterally revoke a notice to withdraw from Article 68 VCLT: the necessity of relying upon a customary incarnation of (or at least elements of) Article 68 VCLT when its customary status is, to put the case at its highest, by no means clear; and the fact that the treaty-based regime in Article 50 is the applicable lex specialis, in this case to the exclusion of any customary regime of procedure for treaty withdrawal. As such, the stronger argument is that an Article 50 withdrawal notification may not be unilaterally revoked by the Member State concerned.

Beyond the legal arguments, it is to be emphasised that the decision to make an Article 50 notification is not one that should be taken on the basis that, if the negotiations are not going to script for the UK, there is a possibility that the process could simply be unilaterally stopped. Basing such a fundamental decision on the chance that highly technical legal arguments might step in and save the day risks creating further uncertainty and undermining the negotiating position of the UK. The blinkers should be removed and the political realities understood; pushing the big red button marked ‘Brexit’ is a step of unquestionable gravity that may not be so easily undone.

Jake W. Rylatt is a College Research Associate at Wolfson College, University of Cambridge. Gratitude is expressed to Jed Odermatt and Joe Tomlinson for their comments on an earlier draft of this post.

(Suggested citation: J.W. Rylatt, ‘The Irrevocability of an Article 50 Notification: Lex Specialis and the Irrelevance of the Purported Customary Right to Unilaterally Revoke’ U.K. Const. L. Blog (27th July 2016) (available at:

3 comments on “Jake Rylatt: The Irrevocability of an Article 50 Notification: Lex Specialis and the Irrelevance of the Purported Customary Right to Unilaterally Revoke

  1. Mike Fearon
    July 27, 2016

    The use of the terms “save the day” and “big red button” may tell a story here. The contrary arguments are well made, but there are strong political arguments in favour of (and against) the government favouring executive action. A decision to invoke Aritucle 50 by executive action is unlikely to be taken with a fallback position of “saving the day” in the government’s collective mindset. The government may consider whether a domestic legal challenge could cause difficulties and necessitate some kind of parliamentary approval prior to notice. These contrary arguments provide support to proponents of the possible courses of action which the government may pursue. I am not convinced that Mr. Rylatt’s argument is strong enough to persuade a court that sufficient grounds exist for legal intervention in the process. Mr. Streeten’s arguments, however, may be strong enough to achieve a contrary view.

  2. Denis Cooper
    July 28, 2016

    It seems to me that as the EU treaties set out no clear legal path the other member states would take an ad hoc political decision on their response if a country wanted to rescind its notice that it intended to leave the EU. I very much doubt that they would wish to involve the ECJ with all the delay that would entail, and they may not even ask their legal service to look for precedents around the world.

    And I would expect their response to partly depend on how much time and effort they had expended following receipt of the Article 50 notice.

    At one extreme if a member state put in its notice in the morning but then some hours later said that it was a mistake, or that after an emergency meeting it had changed its mind, then the President of the European Council might think that he hadn’t yet acted on the notice so he would just allow it to be revoked.

    On the other hand the governments of the other member states would be unlikely to take kindly to a country saying it had changed its mind after two years had been spent on hard negotiations.

    Then they might say “Tough, you said you wanted to leave and so you must leave, if you like you can apply to re-join afterwards”, or they might say “OK, you can stay, but we want this price for our trouble” – which in the case of the UK might be surrendering its existing treaty opt-outs.

    It seems very unlikely to me that they would just say “Great! We’re so glad you’ve decided to stay after all, now let’s just forget all about it and carry on as if you had never put in your notice that you intended to leave”.

  3. Pingback: Brexit Basics 6: update 30th July | Law & Religion UK

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