The Referendum on whether Britain will stay in the European Union or not will take place on 23 June 2016.

If the Referendum results in the UK Government handing in to the European Council the notice pursuant to Article 50 (2) of the Treaty on European Union (“TEU”), then the exit process provided for in Article 50 TEU will be started and the UK and the EU would enter into negotiations in respect of a Withdrawal Agreement. The UK would cease to be a Member State of the EU either at the date at which the Withdrawal Agreement enters into force or , if there is not yet a Withdrawal Agreement which has entered into force, two years after the notice pursuant to Article 50 (2) TEU has been received by the European Council.

Even before the vote takes place politicians, academics and lawyers are arguing about how certain key aspects of any Brexit may work. One such area of dispute is what happens if the UK Government changes its mind about a Brexit during the two year notice period. It is perfectly feasible that a close vote on the referendum (either way) could lead to a change of UK Prime Minister and following a General Election, a change of the political leaning of the Government. Such changes could lead to a desire by the Government of the day wanting to unilaterally revoke the Brexit notice.

Until recently it had been the widely held view across Europe that any termination notice by the UK Government to the European Council cannot be revoked unilaterally since the wording of Article 50 TEU is said to be clear, does not provide for a revocation right and provides that the termination notice kick-starts the two years negotiation period which automatically results in the relevant Member State leaving the EU after such two years unless an extension of the two year period is agreed unanimously. This view has, for example, been set out in a research paper of the European Parliament published in February 2016.

In contrast to the view proposed in the research paper of the European Parliament, on 4th May 2016 the European Union Committee of the House of Lords issued a report in which it proposes a contrary legal view that a withdrawal notice can be revoked unilaterally during the two years negotiation period. This report is based on a public evidence session which the committee held with Sir David Edward, QC, and Professor Derrick Wyatt, QC.

It should be noted that neither report discusses whether and to what extent Article 68 of the Vienna Convention on the Law of Treaties – which provides that certain notifications which target at ending International Treaties may be revoked at any time before they take effect – could become relevant for the interpretation of Article 50 TEU. In addition neither report considers how Article 50 TEU should be interpreted, in the light of the autonomous approach which the European Court of Justice takes in respect of interpreting European law independent from the individual domestic approaches of EU Member States and which might disregard Article 68 of the Vienna Convention.

So all we can say for the time-being is that the ability of the UK Government to change its mind on Brexit is yet another area of uncertainty on which the Brexit and Bremain sides of the Referendum debate – as well as different groups within the Brexit and Bremain sides – will no doubt take diametrically opposing views.