Brexit: Who can pull the Article 50 trigger?

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By Kristyna Muhlfeitova on

Theresa May and David Cameron are wrong


David Cameron: “I think it’s right that this new Prime Minister takes the decision about when to trigger Article 50.”

Theresa May: “I will not trigger Article 50 until 2017.”

Are Cameron and May right in assuming they can trigger Article 50 alone without parliament? What is the power that allows them to do so?

There are two main, clashing opinions in response to these questions. One camp claims new legislation is needed to authorise the government to trigger Article 50; the other camp claims the government may trigger it using royal prerogative without any legal need for parliamentary involvement.

These opinions have their flaws.

Instead, I lean towards a third, less mainstream opinion, first proposed by Robert Craig, an academic at LSE, who argues a statutory power already exists authorising the government to trigger Article 50. However, I don’t agree with all of his suggestions.

First, let’s look at the problems with the main interpretations.

Both the ‘new legislation is needed’ camp and the ‘prerogative’ camp rely on the assumption there is no existing statutory power authorising the government to send the Article 50 notification.

But, as it has already been pointed out by Craig, Article 50 has been incorporated into domestic law: The European Union (Amendment) Act 2008 incorporates the Lisbon Treaty — a part of which is Article 50 — into domestic law. It inserts the Lisbon Treaty into s1(2) of the European Communities Act 1972. Consequently, the principle in AG v De Keyser’s Royal Hotel — which established that if there is a statutory power, the statutory power has to be used instead of the prerogative — stops the government from using the prerogative. Instead the statutory power must be used. Hence, the government may make the official notification of withdrawal under Article 50.

However, Craig is wrong to subsequently conclude that no parliamentary debate is legally needed. After having a closer look at Article 50, it becomes clear a statutory power authorising the executive to send a formal notification is not enough to trigger Article 50.

There are two parts to the Article 50 notification:

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.

The first part places an obligation on the Member State to make sure the decision to leave satisfies the constitutional requirements of the Member State and the second part places an obligation to communicate the decision to the European Council formally.

Hence, in order for a notification to withdraw to be valid, a decision to withdraw must be first made in accordance with the constitutional requirements of the Member State.
In the context of the United Kingdom, it is the government that may make the formal notification under statute (The European Union (Amendment) Act 2008). However, to satisfy the constitutional requirements for a valid decision under Article 50, a vote in the House of Commons is needed.

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The constitutional requirements are made up of constitutional principles and conventions. It is true that conventions are not usually enforceable in courts, however since the UK constitution is very scattered, these principles and conventions form a part of the constitution.

Professor Mark Elliott has pointed out that not following a non-legally binding convention is still considered unconstitutional, although not necessarily illegal. Nonetheless, these conventions and principles become legally binding in the context of Article 50, since Article 50 demands constitutional requirements be met, not legal constitutional requirements.

There are three main reasons why it would be unconstitutional and consequently legally ineffective for the executive to make the decision to trigger Article 50 without parliamentary involvement.

Firstly, the UK constitution is based on parliamentary sovereignty and the separation of powers. Preventing parliament from having a say in triggering a process that would significantly distort an important part of the constitution would take away power from parliament and contravene its sovereignty. Moreover, when considering the doctrine of the separation of powers, it is clear the government and parliament have different roles in this process. The function of the executive is to control foreign affairs, and it is the function of parliament to debate issues. In the Brexit scenario, it is the function of the executive to conduct the negotiations with Brussels and to officially trigger Article 50. On the other hand, it is the function of parliament to debate the decision of when and if to opt out of EU treaties.

Secondly, there is a constitutional convention for parliamentary involvement on issues of great importance. For example, there is a strong convention for a vote in the House of Commons before the deployment of armed forces abroad (as there was in relation to involvement in Syria in 2013 and 2015). This expectation for a vote in the House of Commons exists to ensure the executive does not have a lot of unfettered power over serious decisions; the vote in parliament serves as a check and balance and ensures accountability. Hence, it is not clear why a convention such as this one should only be constrained to that one context and should not apply in a case where a similar (or even more important) decision is being made. And anyway, there is already a precedent in the context of decisions made in relation to EU law. There was a parliamentary debate in relation to the UK opting out of several measures in the Lisbon Treaty which signifies the wider scope of the convention.

Lastly, the result of the referendum is not constitutionally binding and cannot form the sole basis of the decision. Jo Murkens, a professor of public law at LSE, correctly points out that parliament could have made the referendum legally binding just as it made the result of the 2011 referendum on electoral reform binding. Instead, parliament purposively chose not to in order to preserve parliamentary sovereignty. Hence, given parliament’s purposive intention not to bind its hands by the referendum, the referendum itself is not a decision in the sense of a ‘decision to withdraw’ under Article 50, as it does not conform to the constitutional requirements.

At its most basic, the UK is a parliamentary democracy and not a direct democracy: those who make decisions are elected representatives, not the people, in a referendum. The referendum was to advise the legal representatives in a debate about the issue, not to replace their function. If representatives were there merely to reproduce the decisions of the electorate they could not be held accountable for the decisions of parliament. It is up to the representatives to debate the issue and conclude what is in the national interest.

Moreover, as Murkens points out given the devolution treaties, the constitutional structure of the UK has split the UK into four constituent parts of England, Wales, Scotland and Northern Ireland. He argues the referendum was a draw of a 2:2 split with England and Wales voting to leave and Scotland and Northern Ireland voting to stay. To ignore the vast regional differences and take the referendum result as a ‘decision’ would fundamentally undermine the structure of the UK and would not conform to this constitutional requirement.

So, who has the power to Brexit?

The answer: the government has a statutory power by virtue of the European Union Act 2008 which incorporated Article 50 into domestic law, to send the official notification under Article 50. However, the notification under Article 50 will only be valid if the decision to withdraw is made within the UK’s own constitutional requirements as demanded by Article 50. These constitutional requirements include even usually non-binding conventions and constitutional principles since there is no requirement for them to be legal requirements. The conventions and constitutional principles of the UK point towards the conclusion that for the decision to be valid, a vote and a debate in the House of Commons is needed. May and Cameron were wrong.

Kristyna Muhlfeitova is a second year law student at the London School of Economics.


Jowell J, Oliver D and O’Cinneide C, The Changing Constitution (8th edn, Oxford University Press 2015)

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