If you’ve been following closely news about Britain’s EU referendum and its aftermath, you’ll probably have heard of article 50 of the Treaty on European Union which makes provision for a member state to leave the EU and lays down an extendable two-year period for a withdrawal agreement.


Here it is:

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 If a State which has withdrawn from the Union asks to rejoin, its request shall be subject to the procedure referred to in Article 49.


There’s some debate going on between lawyers and in the media on various legal questions about the article 50 process. Is the government legally obliged to “trigger” article 50? Can it legally do so without a Parliamentary vote? Can the EU take the view that the referendum itself “triggered” article 50? Can article 50 be circumvented, and the UK leave by some other legal means? Can the EU throw us out? Can the UK decide unilaterally when article 50 is “triggered”, if it ever is? I’ll tackle all these questions.


The EU Referendum Act 2015 creates no legal obligation on Her Majesty’s Government to leave the EU now, or ever. In a legal sense, the Act was binding in the sense that ministers had a duty to hold it; but the referendum is not binding in the sense that they must do anything about its result. The force of the result is political.  It follows that the UK can “trigger” it if and when it likes.


David Allen Green has written about what might in domestic constitutional terms represent a “decision to withdraw” from the EU. It seems to me that the really key step under article 50 is the notification that would (I agree with David on this) be made by some sort of formal communication from the UK government to the European Council, probably a letter from the UK’s Permanent Representative in Brussels to the European Council President, Donald Tusk. In my view the European Council must wait for this step. It cannot “look inside” British constitutional law and decide for itself when the UK has decided to withdraw. All it can properly do is recognise when a step is taken in EU law—that is, the article 50.2 notification if it ever comes.

That does not mean, however, that the UK can simply dictate the timetable, taking as long as it likes for talks and notifying under article 50 when it’s good and ready. That impression was given by Vote Leave, but it was always a naive idea. An elementary point about negotiations is that you can’t actually force anyone to bargain with you. The EU can, therefore, decide that it will only do so once an article 50 notification is made. Unsurprisingly, that seems to be an attractive stance in Brussels and other European capitals. The upshot is that the UK does, in practical terms, have to trigger article 50 if it wants to leave the EU.

What I imagine may happen in reality is that the EU enters into informal preliminary talks once a broad timetable is agreed, including a date for article 50 notification.


Not really. Vote Leave argued that the UK could leave under article 48 of the TEU or under article 54 of the Vienna Convention on the Law of Treaties. But either would require the consent of all other EU member states. The UK simply cannot insist on using them rather than article 50.

It is worth noting, though, that the UK could be thrown out of the EU by the other member states under article 60.2 of the Vienna Convention if it was guilty of a “material breach” of its treaty obligations—which, it’s important to realise, will apply after article 50 notification right up to the moment the UK actually withdraws. The relevant parts of article 60(2) and (3) read:

2. A material breach of a multilateral treaty by one of the parties entitles:

(a) The other parties by unanimous agreement to suspend the operation of the treaty   in whole or in part or to terminate it either:
(i) In the relations between themselves and the defaulting State, or
(ii) As between all the parties; …

3. A material breach of a treaty, for the purposes of this article, consists in:

(a) A repudiation of the treaty not sanctioned by the present Convention; or

(b) The violation of a provision essential to the accomplishment of the object or purpose of the treaty.

The European Union Law (Emergency Provisions) Bill promised by Vote Leave even before the UK negotiated its withdrawal might well constitute a material breach, given that it’d mean refusing to recognise the jurisdiction of the European Court of Justice. Being thrown out wouldn’t be very attractive, as it’d mean there’d be no agreement for instance about the protection of the rights of British companies and citizens elsewhere in the EU.


In terms of domestic constitutional law, the government may choose to ask Parliament to vote in favour of article 50 notification—but there is no legal or constitutional requirement on it to do so. Notification would be (in domestic law terms) be done under prerogative powers in relation to international affairs, rather than any statutory authority. The government can just go ahead and do it.

Nick Barber, Tom Hickman and Jeff King have ingeniously argued that government cannot do this alone because of the principles paid down by Coke CJ in the seventeenth century Case of Proclamations and more recently by the House of Lords in R v HomeSecretary, ex parte Fire Brigades UnionTheir argument’s interesting, but it won’t wash.

The European Communities Act 1972 (which imports EU law into our domestic legal system) would continue to apply unamended after article 50 notification, which would not therefore alter common law, or statute, or “the customs of the realm”. Nor would it create any criminal offence. The Case of Proclamations simply isn’t relevant.

Nor is the FBU case a precedent here. In that case, an Act of Parliament had laid down a detailed statutory scheme of compensation (as it happens, for people injured as a result of criminal offences; but that detail’s not important for our purpose). Parliament gave a government minister discretion about when to bring those provisions into force. The House of Lords ruled that this didn’t give the minister a legal duty to bring the provisions in; but it did mean he could not use prerogative powers to introduce a wholly different scheme instead of the one Parliament had laid down. The existence of the discretion granted by Parliament meant the prerogative was limited or ousted to that extent.

The situation as regards the European Communities Act 1972 and article 50 notification is very different to the situation in the FBU case, however. The ECA 1972 does not confer on ministers any similar kind of discretion to bring or maintain its own provisions in force, so there is no FBU-style statutory limitation on or “ouster” of the prerogative power to notify.

Nor would notification render the 1972 Act a “dead letter” or render it “nugatory”, as Barber, Hickman and King argue. On the contrary, it would remain fully in force until repealed by Parliament. It’s not even obvious that it’d be repealed on Britain’s eventual withdrawal since, at least according to what Boris Johnson has recently written, Britain might end up abiding by elements of the Agreement on the European Economic Area—which is one of the treaties having effects in our law under the 1972 Act. It’s simply not right to see article 50 notification as negating the 1972 Act, or as hindered by it.

What the House of Commons can do, if it doesn’t like government policy on article 50, is pass a motion of no confidence in the government which (depending on its precise terms) might force the government to resign or else bring about a general election, under the Fixed-term Parliaments Act 2011. Now may be the time to remind you that I wrote an e-book about that Act, which may be tested during the current crisis.


It’s up to the British government alone whether and when to “trigger” article 50. It may ask for Parliament’s approval, but isn’t legally required to. What Parliament can do is force the government to resign or force an election.

It’s not realistic to try to leave the EU in any other way—all we could do to circumvent article 50 would be to get ourselves thrown out without any agreement. And Britain can’t dictate the article 50 timetable. It can delay notification under article 50; but the EU can simply refuse to negotiate with Britain until notification.

Let’s see if it ever happens.