Does Article 50 require an Act of Parliament? A brief thought-experiment.

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Here is a question: would a decision by the United Kingdom to withdraw from the European Union require an Act of Parliament?

On this question, one week or so after the referendum vote for Leave, it may be fairly said that “views differ”.  Some constitutional lawyers say one thing, others say the other.

In favour of an Act of Parliament being the only way, see David Pannick in The Times, Nick Barber, Tom Hickman and Jeff King on the UK Constitutional Law Association site, and Adam Tucker at the same site.

In favour of it being just one means among others, see Carl Gardner at Head of Legal and Mark Elliott at Public Law for Everyone.

When the views of experts differ it is a temptation to just shrug with despair.

Nobody would blame you.


This post sets out a contention – based on a thought-experiment – that an Act would not be required.

An Act could be a means of the decision being made – on that point views do not differ – but it is not the only way.

What follows is that contention – but please note this post is a (minor) contribution on one side of a debate rather than an (attempt at) objective exposition of an area of controversy.


First, let’s remind ourselves of the relevant parts of the first two paragraphs of Article 50 (I have omitted some not relevant text):

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 key question is what is a “decision” in accordance with the UK’s “own constitutional requirements”.


Second, let’s consider a thought-experiment based on a counterfactual situation.

Think back to last Friday, the day the result of the referendum came in.

Consider now the following facts:

– a national referendum had taken place in accordance with a statute passed for the sole purpose of that referendum;

–  33,577,342 voters voted in that referendum (72% of the electorate);

– there was a clear (if narrow) vote in favour of Leave;

– the Prime Minister had said expressly at the beginning of the referendum campaign that “If the British people vote to leave there is only one way to bring that about – and that is to trigger Article 50 of the Treaties and begin the process of exit. And the British people would rightly expect that to start straight away”; and

– the government had expressly stated during the campaign “This is your decision. The government will implement what you decide”.

Taking these five facts, imagine now the Prime Minister (by himself or after consulting with Cabinet) taking the decision (or purporting to take that decision) on that Friday that the UK had decided to withdraw from the European Union in accordance with its own constitutional requirements.

There had been a special referendum passed by Parliament for the purpose, there had been a heavy turn-out and a decisive result in the vote in that referendum, and the government had stated clearly that the decision would be implemented and the Article 50 straight away.

Imagine now the Prime Minister that same Friday had been minded to notify the European Council of such a (purported) decision.

What would be the legal position if some wily litigant- lets call her Ms Haddock – had been quick enough to make a legal challenge that same day?

I cannot see how the courts would have seen the claim as justiciable: there had been a special referendum with a clear result on a high turn-out and the government had moved to implement the decision straight-away as it clearly stated it would do.

Even if the court had allowed Ms Haddock’s claim to be heard, I cannot see how it would have quashed the decision or injuncted the Prime Minister from notifying the European Council.

Not only would there have been an uproar as the courts blocked the popular decision (and significant economic instability), one suspects the courts would have said that to interfere in the decision and the notification would be a violation of the separation of powers.

Our litigant Ms Haddock would have lost.

In other words: for the Prime Minister (with or without cabinet) to make such a decision and notification would not be unlawful.  It would thereby be lawful.


The thing about questions of law is that the legal position on day one should normally be the same as the legal position on day ten, if the law and the facts are the same.

If so, then if the Prime Minister today – or in September, or whenever – took the same decision and made the notification then it would be just as lawful on day ten than on day one (assuming the law or facts have not changed).

As a normative view, I agree that an Act of Parliament (or a resolution or motion in Parliament) should be the method: the referendum was not legally binding – whatever the government said – and such a significant decision should be made by Parliament.

A vote by Parliament would also provide convenient cover for a government reluctant to press the Article 50 button.

(It may well be that the legal position changes, and Parliament passes a resolution or motion that the final decision has to be made by itself.)

But I cannot see how a decision on notification made by the Prime Minister on the day of the referendum result itself would have been quashed or injuncted by the courts, had Ms Haddock brought a claim to block it.

If that was true on that day, that would be true now, all other things being equal.

And if this is correct, then presumably an Act of Parliament is not the only means by which the Article 50(1) decision can be lawfully made.


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