Whether the UK can cancel its exit from the European Union, or requires approval from the heads of state and government of the EU member states to do so, has undoubtedly great political importance. But this is first of all a legal question of EU law.
The Court of Session, Scotland’s highest court, has now referred to the European Court of Justice (ECJ) for a binding ruling on the question of whether an EU member state can unilaterally revoke its notification under Article 50 of the Treaty on the European Union (TEU) before the end of the notice period of two years.
The ECJ is hearing the reference (Case C-621/18) in an expedited procedure, and its Advocate General is to give a non-binding advisory opinion on 4 December.
The following analysis argues that, from a strictly legal point of view, an EU member state may indeed revoke its notification freely. Article 50 TEU has to be read in the light of international treaty law, which gives the clear answer that unilateral revocation is possible in the overriding interest of treaty integrity.
It is widely accepted that the Founding Treaties of the European Union are and remain international law between the member states, regardless of the quasi-constitutional law properties that EU law has acquired over the years.
The ECJ has made that point again in its recent Achmea judgment of March 2018 (Case C-284/16, at para 150). As such the Treaties are governed by the body of international law that governs all treaties, which is codified in the 1969 Vienna Convention on the Law of Treaties.
This convention is binding on all the member states of the EU, as well as on the Union itself as so-called customary international law.
The convention provides rules on the entire life-cycle of a treaty, from conclusion, through interpretation and application, to its termination. Part V deals extensively with unilateral withdrawal (or exit) of one state party from the treaty.
It provides a strict procedure: A State must have right to exit under the treaty, it must then formally notify its intention to withdraw triggering a notice period, and at its expiry exit becomes effective and the treaty ceases to bind the parties.
Crucially, the convention stipulates as follows: ‘A notification …may be revoked at any time before it takes effect’ (Article 68).
The text of the Vienna Convention is hence exceedingly clear. The exit-minded state retains the discretion to revoke the notification, and thus to stop the process up the last minute of the notice period.
It does not require approval from the remaining state parties. This may appear a surprising proposition: surely, the remaining states will have started to make preparations for the exit, and these will turn out be futile.
This very point was indeed considered by the UN body that drafted the Vienna Convention, the International Law Commission, but ultimately rejected.
The commentary of the ILC on its 1966 Draft Articles on the Law of Treaties, the single most valuable source on the meaning of the articles of the Vienna Convention, confirms: encouraging revocations was the overwhelming consideration in the interest of treaty integrity (ILC, Final report, 1966 YBILC 173–274, 264).
The notice period then serves primarily as a cooling-off period, leaving the withdrawing state time for reflection.
The Treaty on European Union is concluded and terminated just as other treaties in international law pursuant to the Vienna Convention. Article 50 TEU, the clause for withdrawal from the Treaty, is generally closely moulded in the template of Part V of the Vienna Convention.
There are, however, some gaps in drafting, and the clause contains no equivalent to Article 68 of the Convention.
How is this gap to be closed? The best view is to refer and read Article 68 of the Vienna Convention into the Treaty on European Union. Part V of the Vienna Convention is adamant that its provisions on withdrawal are prescriptive for all treaties, including the EU Treaties.
And the records of the European Convention, the EU body that drafted what was later to become the clause on exiting from the European Union, show that it intended to fully follow the template of the Vienna Convention.
This is also implicitly recognised by the draft EU-UK Withdrawal Agreement. It deals with surviving financial obligations and individual rights in just the way Article 70 of the Vienna Convention prescribes even though Article 50 TEU has another gap in drafting there.
The burden is then on those that argue that a deviation from the Vienna Convention was intended. But the possible arguments are not convincing.
The overriding consideration of treaty integrity justifies incentivising an EU member state to change its mind and not to leave, indeed up to the last minute. That applies here as for any other treaty, and maybe even more for treaties constituting international organisations such the European Union.
Nor need there be concern that a member state may start playing repeat games. It would be contradictory and hence impermissible to revoke and then notify again on the same facts such as a referendum.
By Volker Roeben, professor of Energy Law and Global Regulation at the Centre for Energy, Petroleum and Mineral Law and Policy at the University of Dundee.