Brexit Brief: Article 50

What is Article 50 of the Lisbon Treaty?

Article 50 is the only legal mechanism for a member state of the European Union (EU) to leave. A short paragraph in the Lisbon Treaty agreed by all EU member states in 2009, it sets out the steps a country needs to go through to withdraw from its treaty obligations.

Who can trigger Article 50?

Only the UK Government can decide to trigger Article 50; it can’t be forced to do so by the other EU states. The decision could be made by the Prime Minister alone in accordance with the ‘royal prerogative’ over foreign affairs, or in consultation with her Cabinet. Theresa May has said that Parliament will have a chance to debate the triggering of Article 50 before the decision is made. However, she has emphasised that the final decision is for the UK Government and that Parliament will not have a chance to make a binding decision on the matter. The courts are currently considering a number of cases arguing that Parliament should have such an opportunity. 

How can Article 50 be triggered?

The first step is for the UK Government to take a decision to leave. The referendum was not a decision for the purposes of Article 50 – legally it was non-binding – communicating the will of the British people to the Government.

It is only once the Government makes a formal decision that they are required to notify the European Council. This would be done by the Prime Minister, either orally at a meeting or in writing. It cannot be done accidentally – it must be a formal act explicitly intended to trigger Article 50.

When will Article 50 be triggered?

Theresa May has said that she will trigger Article 50 by the end of March 2017.

Does Parliament have a formal role in triggering Article 50?

The Government’s view is that the Prime Minister can take the decision to trigger Article 50 in accordance with the ‘royal prerogative’ over foreign affairs.

However, several legal experts have disputed this and argue that Parliament must consent to the triggering of Article 50. Some argue that a vote on a substantive motion would be sufficient, while others argue that primary legislation is required.

The experts concerned argue that the Government cannot use its prerogative power to remove rights or repeal or amend existing statute (unless given explicit powers to do so). Triggering Article 50 would set in motion a process that would inevitably result in the UK ceasing to be a member of the EU. This would mean that the 1972 European Communities Act, which Parliament passed in order to give EU law effect in the UK, would have to be repealed – a process the Prime Minister has said she intends to begin in 2017. It would also remove the rights of British citizens to vote and stand in European parliamentary elections. The court cases underway, and subsequent appeals, are expected to conclude by the end of 2016.

This Brexit Brief was last updated on 17 October 2016.


Article 50

1. Any Member State may decide to withdraw from the Union in accordance with its own constitutional requirements.

2. 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. It shall be concluded on behalf of the Union by the Council, acting by a qualified majority, after obtaining the consent of the European Parliament.

3. The Treaties shall cease to apply to the State in question from the date of entry into force of the withdrawal agreement or, failing that, two years after the notification referred to in paragraph 2, unless the European Council, in agreement with the Member State concerned, unanimously decides to extend this period.

4. For the purposes of paragraphs 2 and 3, the member of the European Council or of the Council representing the withdrawing Member State shall not participate in the discussions of the European Council or Council or in decisions concerning it.

A qualified majority shall be defined in accordance with Article 238(3)(b) of the Treaty on the Functioning of the European Union.

5. If a State which has withdrawn from the Union asks to rejoin, its request shall be subject to the procedure referred to in Article 49.