When the European Union member states drafted and then approved the Treaty of Lisbon in 2007, they did not think anyone would ever want to leave ‒ it was a few years before the Eurozone crisis, and the bloc was still glowing from its watershed expansion eastwards.

So when, for the first time in its history, the EU included an article – the now-infamous Article 50 ‒ for a potential exit, they left it deliberately vague.

“The Treaty of Lisbon was drafted with the idea that [Article 50] would not be used, and to make it pretty hard to exit in a smooth way,” says Chris Bickerton, a lecturer at Cambridge University and author of The European Union: A Citizen’s Guide.


What this means in practice now is days, weeks and even months of political uncertainly as all sides try to work out how to interpret the treaty.

Here is what is spelled out explicitly in Article 50:

A government must trigger the article by officially notifying the EU of its intention to leave. Then there is a two-year period in which the terms of the leaver’s exit are negotiated.

During this time Britain would no longer be able to take part in any EU decision-making, and any exit agreements must be approved by all 27 remaining EU nations and the European Parliament. Then after Britain’s formal exit, fresh negotiations can begin on any new trade deals. 

But crucially, there is no timescale or mention of when to trigger Article 50 after a referendum, leaving many politicians worried about a long period of uncertainty.

Even after the issue of the triggering of Article 50 is resolved, the British government must then decide its negotiating position, and decide what sort of relationship they want with the EU in the future. Would they still want access to the single market? What status would they want for the EU citizens currently employed in Britain, and Britons working elsewhere in Europe? What sort of trade deals would they wish to pursue? These proposals would then be put to the other 27 EU member states.

It is a process which European Council President Donald Tusk has warned could take up to seven years, and it is likely to be a bitter fight.

“There has to be some sort of deterrent that the other 27 member states now need to build into this so that there is a clear message that this is not an attractive model,” says Mr Techau.