Article 50 of the Lisbon Treaty

Article 50 of the Treaty on European Union is a part of European Union law that sets out the process by which member states may withdraw from the European Union. It has been extensively debated after the referendum held in the United Kingdom on 23 June 2016 in which 51.9% of those voting favoured the United Kingdom's withdrawal from the European Union.

Once Article 50 is triggered, there is a two-year time limit to complete negotiations. If negotiations do not result in a ratified agreement, the seceding country and EU would follow World Trade Organisation rules on tariffs.

This article was used for the first and so far only time by the United Kingdom on 29 March 2017.

Article 49A of the Treaty of Lisbon, which came into force on 1 December 2009, introduced for the first time a procedure for a member state to withdraw voluntarily from the EU. This is specified in Article 50 of the Treaty on European Union, which states that:

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

Article 50 of the Treaty on European Union provides that: "Any Member State may decide to withdraw from the Union in accordance with its own constitutional requirements." Once a member state has notified the European Council of its intent to leave the EU, a period begins during which a leaving agreement is negotiated setting out the arrangements for the withdrawal and outlining the country's future relationship with the Union. A withdrawal agreement would then be negotiated between the Union and that State.

In an opinion piece, The Guardian explained that Article 50 could be invoked only by an individual departing EU member country and that the treaty obligation for the EU to negotiate was not activated until formal notification was delivered.

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