Brexit: Who can pull the Article 50 trigger?

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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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Cue Not Amused incoming with his Brexiteer rantz in 3…2…1…


I could be wrong but I’m pretty sure Not Amused is a lady..?

a) indicating a preference to be compared to to Phylida Trant not Erskine-Brown
b) getting quite irked that a comment I made about our beloved Prime Minister.. (*cough*) riding a broomstick was misogynistic*..

[* – not how it was intended in point of fact]
I’m not Sherlock Holmes but seems to point to this ?


Also there have been NA references (too lazy to dig up links) to most people getting her gender wrong, and also to her wearing high heals.


NA on high heals?

Mind: blown.


It’s heels btw.


Do Trolls have a gender?


Yes, I always thought they were a bit like those strange underwater creatures that reproduce by division…


I have it on good authority that Not Amused self-identifies as a rotten haddock


2nd year? Good luck passing if this is your writing style.


A tad harsh, it is only a few days into the term no doubt she will improve.


This article is interesting but hard to follow. Nice mention of the LSE Law Professor though who is based at the same institution where the author is studying may win a few points on the next assessed bit of work.

Tory Powerhouse

These kinda people populate LSE these days? No wonder that university is going down the tubes.


Oh the ironing….

“kinda” – ?
“that university” – is a constituent college of the University of London is it not ?



I think you forgot the washing too. And the dusting.


Oh dear. Further ironical chuckles to be had…

When I grow up I want to be a trainee at Irwin Mitchell

Agreed, this article is a load of hogshit.


I thought this was excellent and well-structured


Hi Kristyna!


Lol what are you smoking, this article sux ballz 😂😂😂


Just like yo mama then

When I grow up I want to be a trainee at Irwin Mitchell

So original, you must be a smart boy.

Travelling Gavel

The use of sentence structure and syntax is somewhat lacking…

“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. “

Slaughter and Gay

Obviously English as a second language.

I do luv me some Eastern European gash tho… Mmmm…


You serious bro? Check out her FB, she’s fugly as.

Not Amused

I’m not sure that I want to live in a country where unelected judges can say that two separate Prime Ministers are wrong. Just on a basic principle.

On your first argument, I’m not sure I recognise the distinction. Parliament will have a role on the laws we adopt/don’t adopt. But fundamentally they don’t negotiate treaties nor implement them. It would be an odd country that let Parliament negotiate a treaty – herding cats is easier.

I don’t necessarily believe Blair giving the House a vote on Iraq and Cameron giving one on Syria means that all foreign policy prerogative powers have been ceded to Parliament either. A genuine question is – did the Lords debate/vote on Iraq? Because I don’t recall them doing so. In which case wasn’t the vote in the Commons more an act of solidarity than a cessation of prerogative power? I think the Lords didn’t vote on Syria either.

Constitutionally I think it is quite odd to say “well Parliament is sovereign” and then ignore the fact that Parliament has 3 parts – commons, lords and the Queen. If only 1 part was involved then while a journalist might say ‘parliament’ a lawyer oughtn’t.

In any event I’ve never seen the Commons vote on a non military foreign treaty that I am aware of. Not on trade or cooperation etc. Is the author saying that every new trade deal will have to be approved by parliament?

I think the oft spouted ‘non-binding’ point is fatuous and is the preserve of non-lawyers who say silly things like ‘an oral contract isn’t worth the paper it is printed on’. Oral contracts are fine. A PM during a debate saying he will implement the conclusion is pretty clear to me.

But the ultimate conclusion is that none of this matters. Parliament (all 3 parts) if given a vote would have to implement the referendum decision. To do otherwise would lead to a fresh election (and a landslide Tory win with deselection for a handful of Tory MPs who are still remainiacs) and huge reform of the Lords as we sacked most of them. It would also put her Majesty in a pickle as she wouldn’t want to be anywhere near anything that would be so obviously unpopular.

Most Remainers are decent and have accepted the result. Those interested in finance should seek out the views of Mervyn King and Martin Lewis. There are really only a very small amount of die-hard remainers who keep making a fuss and they do look anti-democratic and rather cult like. Given the EU is obviously in a very bad state, it’s not immediately clear what this small minority is so passionate about having lost. It’s starting to look more like narcissism to me


Hmm, cries foul on unelected judges overturning the PM, then talks up the Queen and the House of Lords’ role in parliament. Interesting contradiction there NA.


What’s wrong with the court acting as a check on the powers of parliament? This is the second post I have seen where you question this – isn’t it proper in a democratic society to have the courts acting to ensure that politicians act properly and within their powers?


Not Amused, as one who knows a little of financial services, I would dearly love to know how you square your “everything will be ok, no it’s ok, there there…” regarding splitting from the EU and the obvious loss of financial passporting ?

Banks will always do what is the cheapest – that’s a fact. So if it becomes more expensive for the likes of JPM, Morgan S, Goldmans, BAML, Nomura etc to headquarter out of London, you can bet your bottom dollar that THAT is exactly what they will do.. Most likely Frankfurt before you can mouth the words “eine kleine Currywurst bitte”…

So, in that scenario, how does the City of London and the rest of the UK economy (all intertwined and irrevocably dependent on) continue to thrive ?

I would be really be fascinated to know your theories on this..

Not Amused

One of the most poisonous aspects of the Remain argument during the campaign boiled down to basically saying “leaving will definitely destroy the world, you are just too stupid to see it”. The reason that argument failed in the nation is that it isn’t very convincing. Real grown ups know the world is not black and white. The world is grey. Nothing is inherently amazing. Nothing is definitely horrendous. Or at least – nothing that anyone votes about.

This is partly why the Remain message resonated so well with children and young people. They are more susceptible to believing the world is black and white. It isn’t. Believing the world is black and white is a comfort blanket for idiots – now Remain has failed, people need to grow up.

Martin Wheatley was the head of the FCA. He was sacked by George Osborne because he said that Brexit wouldn’t impact financial services. Mervyn King is a former governor of the bank of England and he believes financial services will be fine. Martine Lewis is a highly renowned FS expert who supported Remain. He has decided to accept the vote and now says that Brexit will be fine for FS.

So the better question really, is why you think those 3 people are definitely wrong?

No one is going to Frankfurt. Deutsche Bank is having big problems. Commerzbank is worse. The Italian banks have said they have bad debt of 40 to 70%. The ECB keeps changing its rules and doing odd things. Jean Claude Junker just put Latvia in charge of the EU’s Financial Services portfolio. Things look bad for the EU. That’s sad. But true. The Euro is a catastrophic failure. The EU will probably die.

Meanwhile London 1) gets passporting via equivalency and will probably implement MiFID2 anyway, 2) arguably shouldn’t trade with the EU anyway as it’s full of toxic debt, and 3) only does a tiny fraction of total trade with the EU – we are bankers to the world and never joined the Euro.

I hope that helps. The young people who read LC need to start to understand that Leave v Remain was not clear cut. It was not ‘racists v the clever people’. The world is complicated. Brexit might still be a disaster – but I wouldn’t (and didn’t) bet my money on that.

Above all I would drop the patronising tone. There are people like me sitting on TC and Pupillage interview panels right now. Recite some low level ‘Brexit is bad’ mantra and you will suffer. Come up with some original arguments and we might listen. But no – the City isn’t doomed.


“…This is partly why the Remain message resonated so well with children and young people. They are more susceptible to believing the world is black and white.”

This is actually very perceptive. But don’t forget the level of manipulation of the young people in our universities. I suspect the reason that Muhlfeitova published this is because the young are being assessed not on their legal/intellectual skills or knowledge but primarily on their political positions. Despite the fact that as successful barristers we can see how inadequate her essay is, I wouldn’t be surprised if she gets good grades for this kind of stuff – and maybe even prizes.


For that hunka’crap? Ain’t happening mate, a Year 12 student suffering from Down’s Syndrome would write a better article.


I appreciate this is a particularly bad article, but it really is the case that the “leftist”/globalist/Soros-financed element will mindlessly proclaim even the most worthless specimens of their camp to be exceptional talents.


Equivalency is not going to work. They will have no incentive to declare the UK rules equivalent to the EU rules, and in any event there is nothing to stop the EU promulgating new legislation that will mean that there is in fact no equivalency.

Not Amused

It’s bold assertions of opinion as fact that will cause young people to fail in interviews if asked about Brexit.

I recommend against it. If you want to do well then try to avoid adopting a dogmatic approach. Try also to stop predicting the future. No one who has tried has yet succeeded.


The sun will rise tomorrow morning. QED.


Why are you permitted bold assertions of opinion such as “London gets passporting via equivalency” and the rest of us are not? I’m also not looking for a TC or pupillage, just trying to explain to the young people here that many of their fears are well founded.


Yes, and all the oldies were manipulated into thinking Brexit would turn the clock back 50 years and reinstate the empire.


Not sure why you think my post was patronising but err touché…

It’s great that a seasoned member (your words) of the Bar like yourself comes on here and enters into discussion – I’m sure we all appreciate it and can learn from it (I hope that’s not seen as patronising either). However, I should point out that I am not particularly young nor am I seeking pupillage nor a training contract. As for Remain appealing to children ? Really ? You must have had an unusual childhood if you concerned yourself with European integration as I have to admit I certainly didn’t when I was scraping my knees playing football in the street and looking for grasshoppers etc..

But anyway, to your points (again thanks for making them) – I’m afraid to say that I heartily disagree again with most of them. First of all, equivalence is not going to be some silver bullet that solves all of our problems with regard to potential barriers on capital flows (I too have seen the articles I think your basing your assertions from and I simply don’t see it – sorry).

As for MIFID 2, all major financial institutions are already gearing up for this (in fact you could almost argue that it’s the only area that any budget is being stumped up for in these sluggish-getting-ever-more-sluggish times :()). The focus with MIFID2 is on long-needed transparency in transaction reporting and the like – especially in these days when the fear of God is being stuck into people with regard to counterparty risk etc and there is a compelling need to make it straightforward to calculate and record such matters. It’s far more than just another EU Directive – it’s a ticket you need to buy to even stay in the club !

Worst of all is your dismissal of the fact that the UK doesn’t use the Euro. True but totally irrelevant I’m afraid. Take a typical Rates desk in any bank (but let’s say some behemoth American one in London) – what do you suppose does the most business – Gilts or Euro Govt bonds ? Clue: it’s not the former.. Now, what do you suppose in a hard Brexit scenario when this bank can’t even claw the tiny margins it once did on its business due to the extra costs of trading UK-EU ? I refer you to what I said above…

I’m sorry but this is what will happen… This is why on the eve of the vote in June EMEA heads of all of these large foreign investment banks were calling Town Hall meetings to urge their staff to ensure they voted that day !

And this is also why the hard line being taken as vogue now has a lot of people extremely worried. In my ever so humble opinion, they’re completely right to be…


Not Amused

As you say, we’re all going to comply with MiFID2. That gives us equivalency. The end. Trying to pretend we won’t get equivalency is just silly. We are starting from a point where the UK is today 100% compliant. The equivalency regime is designed to allow in regimes which are substantially less compliant than we already are.

As you know, which is why your reply is big on word count but scarce on substance – once we have equivalency that’s it. No problems.

However I have also pointed out that personally I would take steps to insulate our banking sector from what is happening inside the Euro. The whole thing is going to go ‘pop’ and it will end very very badly.

I am broadly bored of these arguments. They come from delusional EU cultists who keep asking you to prove that we aren’t all about to die tomorrow. The fact we awake every morning healthy and well has no impact upon their rather narcissistic religion. Believe what you want. Go buy a tinfoil hat. I had (wrongly) thought you were a young person in genuine need of assistance. Now I see you are not.


OK, I think we’re done here.

Might I just say, however, that it’s most illuminating how your general approach seems to involve labelling everyone who does not subscribe to your view(s) as intolerant.. 😐

Adam Deen

Eat my choad.


Cool journal article brah, made me go and apply to LSE.


Cool comment brah, changed my loyf


The following paragraph makes no sense:

“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.”

Adam Deen

But she studies at a top law school? I thought all people at LSE are geniuses?


Another reference to Article 50 of the Lisbon Treaty, which is, legally speaking, incorrect!!!

Are you able to distinguish between a founding treaty and a reform treaty?


6.5/10, Would Bang.


This post has been removed because it breached Legal Cheek’s comments policy.


No way – deffo no more than a 5 – look at the sourpuss face that could curdle milk

Just Anonymous

Interesting article. However, I’m not convinced.

Firstly, I’m not persuaded by any of the three reasons why it “would be unconstitutional … for the executive to make the decision to trigger Article 50 without parliamentary involvement.”

The first reason confuses me. The right to make/rescind international treaties is a recognised prerogative power. So without some strong authority, I can’t accept Muhlfeitova’s claim that “it is the function of parliament to debate the decision of when and if to opt out of EU treaties.” General appeals to Parliamentary Sovereignty and the separation of powers get us nowhere.

Secondly, the claim that “there is a constitutional convention for parliamentary involvement on issues of great importance” is surely wrong. Plainly, there is probably a narrower Convention that Parliament should be consulted before waging aggressive war. But you can’t extrapolate from that a vague and nebulous Convention that Parliament should be consulted whenever the issue is important. Indeed, the Crown surely retains unfettered prerogative power to wage defensive war (as in the Falklands for instance) where British sovereign territory is under attack. Is this an important issue? Yes. Need we consult Parliament? Not necessarily.

The third reason is that the referendum result is not constitutionally binding. Even if true, I don’t think the conclusion follows. Sometimes, the Crown is bound (by Convention) to exercise the Prerogative (Royal Assent for example.) However, this does not mean the prerogative can be used ONLY when the Crown is bound to so do. Utilising the previous Falklands example, the then government was not bound constitutionally to retake the Falklands. However, this fact did not make it constitutionally illegitimate for them nevertheless to do so.

Similarly, I don’t see anything in the submission that the referendum result could have been made legally binding but wasn’t. It certainly could. It certainly wasn’t. And legislation certainly overrides the prerogative. But the absence of legislation is not legislation.

Finally – not that I need it to dismiss the third reason – but I suggest, in addition, that the result of a public referendum IS constitutionally binding, and Muhlfeitova used the (true) fact that here it was not legally binding to incorrectly conclude otherwise.

Now, moving on from the three reasons, Muhlfeitova further argues that, “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.” I dislike this argument. I dislike it because if Remain had won and Parliament were trying to Leave nevertheless, you can virtually guarantee Muhlfeitova would not be advocating it! Accordingly, I reject this argument for exactly the same reason she would reject it if the situation were reversed.

Finally, Murkens’ argument is in reality a purely normative one: that we ought not to leave the EU without the consent of each of the four nations; otherwise the UK will break up. As a normative argument, this has some legs (although I personally disagree with it.) However as a legal argument concerning what the Crown can in fact do, it goes nowhere.


Your assertion that the referendum result is constitutionally binding is not convincing.

The legislation doesn’t make it so and the PM is only claiming a constitutional mandate by attempting to extend the Salisbury Doctrine thinking to cover the whole of parliament through a claim based on the Conservative Manifesto.

When we look deeper at this Manifesto we see the claim fails as it only states the Conservatives will “respect the outcome” of the referendum. Just what was this outcome?

The only outcome that can be drawn from the referendum was at that particular moment in time 17m UK citizens were not in favour of remaining in the EU, 16m citizens were and 13m citizens were undecided. There is certainly no majority opinion of UK citizens saying the UK should leave.

Parliament must do what millions of citizens expected (whether they voted or not) and debate the referendum to determine what it believes the outcome means and what is in the UK’s best interest.

Just Anonymous

Same point as above. If it were Remain that had won by the 52% – 48% majority, would you be saying any of this?

Of course not! You’d be saying the result should be honoured and that the public clearly expected the result of the vote to determine the matter.

Accordingly, I find your argument thoroughly unpersuasive.


You dismiss my argument by guessing what I’d be saying in a hypothetical situation.

How supercilious you are!

You are a poor guesser too.

Just Anonymous

Why thank you. I always know I’m up against a top legal mind when it resorts to personal insults…


I thought I’d better drop my level to that of your reply for fear you’d not understand.

Should I have just said “ner, ner, whatever!”?


By all means, LC, publish articles written by law students who don’t have English as a first language – but kindly do a grammar/syntax edit first, as any half-decent media outlet would do. Does the blog and the writer no favours, otherwise.


LC’s not half decent, there’s your mistake

Deontay D'shawn Devine

Grammar is reeeeesys bruf. Fukkin culchural impeeeeryalizzzam an’ microagresshans innit. Kill whytey lolol

Tommy's choad

It’s LC buddy, what did you expect?


lol who do you think you are saying stuff like ‘X is wrong’ where X is a leading scholar in this field and you’re just a second year? Why does the LSE seem to consistently breed this kind of ego? Have a day off the condescending tone love.


Gave up half way once I realised that the author is a 2nd year uni student still struggling with the basics of law.

She really shouldn’t be trying to publish anything yet.

Even Mishcon de Reya and arch anti-democratic hack lawyer ‘Lord’ Pannick could produce something better than this miserable brain fart.

Better luck next time trying to defeat the will of the British people.

Willson, LL.B

Wonder what the late great Lords Bingham and Denning would have opined about A50, The “trigger” and the “royal prerogative” powers of TM the PM. Why is she waiting until “end of March”, perhaps even the 1st April 2017, before despatching that “punk” EU to oblivion with her Magnum perhaps she does not “feel lucky”…

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