Prime Minister May announced that she will send a letter to the European Union in 2017 that will result in the United Kingdom’s exit from the EU in 2019. That’s the first simple step for a country to leave the EU – a simple declaration under Article 50 that starts two years or more of discussions about the terms of departure.

But does the British Prime Minister have the authority to speak for the United Kingdom and send such a letter? The Head of State of Britain, after all, is not the leader of Parliament, but the Queen. The Prime Minister is not a President, but the leader of a parliamentary government. Her Conservative Party was deeply split over the Brexit referendum. A majority of the members of Parliament were in favor of remaining in the EU. The referendum was advisory, with no written constitution that would declare it binding. So, what would it take as a matter of British law for a departure letter to be valid?

Already a challenge has been issued: that the answer is a vote of Parliament. Only a majority of Parliament would have the power to speak for the United Kingdom, the challengers argue. And what would happen next?

I put this question to Leonard Hawkes, a leading UK-born attorney who practices in Brussels, Belgium, with the law firm BDD. We were in the chambers of the Luxembourg-based European Court of Justice, the highest court in Europe, which could be called upon one day to consider whether a departure from the EU is valid.


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