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Brexit and the UK’s unwritten constitution

As opinion polls in the UK appear to indicate some momentum towards Brexit, we have pondered, as lawyers, just how easy would it be legally for the UK to withdraw from the European Union.


The answer is largely to be found in Article 50 of the Treaty On the European Union. Article 50(1) states that “any Member State may decide to withdraw from the Union in accordance with its own constitutional requirements”. What are those constitutional requirements in the UK? As the UK’s constitution is unwritten, Parliament is sovereign and if Parliament decides that the UK should withdraw from the EU, then that will be that – the Referendum itself has no constitutional effect as such, at least not in the same way that it would, say, in Ireland, where the country’s written constitution shall be amended only by plebiscite.


What happens then, if Parliament respects the will of the people following a ‘yes’ vote for Brexit? Article 50(2) of the EU Treaty states as follows:


”A Member State which decides to withdraw shall notify the European Council of its intention. In the light of the guidelines provided by the European Council, the Union shall negotiate and conclude an agreement with that State, setting out the arrangements for its withdrawal, taking account of the framework for its future relationship with the Union. That agreement shall be negotiated in accordance with Article 218(3) of the Treaty on the Functioning of the European Union…concluded by the Council, acting by a qualified majority, after obtaining the consent of the European Parliament.”


Article 218 of the Treaty on the Functioning of the EU governs agreements between the EU and “third countries or international organisations”, underscoring that after an Article 50(2) notice to withdraw is served on the European Council, the UK shall for all intents and purposes be treated as outside the EU for the purposes of negotiating the terms of its withdrawal. If agreement cannot be reached on such terms, then by Article 50(3) of the EU Treaty, by default the EU Treaty shall cease to apply to the UK on the date falling two years after the notification of its intention to withdraw. This period can be extended by agreement between the UK and the European Council. For the avoidance of doubt, Article 50(4) of the EU Treaty makes it clear that the UK shall not be entitled to participate in discussions of the European Council in decisions concerning the UK – it may only represent itself.


The question immediately arises, can the UK rejoin the EU at a later date if it so decides? The answer is yes, but Article 50(5) makes it clear that this would be only on the basis of the UK applying to join the EU as a new member, without all of the carve-outs and rebates negotiated to date. Clearly it would not be a simple process to rejoin, particularly as there is unlikely to be much political goodwill left among the remaining Member States for a UK that has divorced itself from the Union.


So, could Parliament decide to ignore the result of a referendum and in effect overrule the will of the people as expressed in a referendum (an idea that has been floated in the British media recently)? The simple answer is, ‘yes’. To do so, however, would clearly be to light the touch paper of popular revolt and it would immediately spark a constitutional crisis. For all practical purposes, a ‘yes’ to Brexit will force Parliament to accede to the will of the people, however grudgingly, and thereupon the “constitutional requirements” of the UK required to withdraw from the EU will be met and a notice of the UK’s intention to withdraw from the EU would follow to the European Council.


After that, how matters proceed is anyone’s guess.



The content of this article is provided for general information only. It is not intended to amount to advice on which you should rely. You must obtain professional or specialist advice before taking, or refraining from, any action on the basis of the content herein.


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