UK: Brexit Judgment: UK Supreme Court Dismisses The Government's Appeal

Last Updated: 15 May 2017
Article by Roger Kennell

Parliament must authorise notice of withdrawal from the EU under Article 50


The UK Supreme Court has yesterday, by a majority of 8-3, dismissed the Government's appeal against the Divisional Court's judgment in November 2016 which held that the Government could not give notice of its intention to withdraw from the EU under Article 50(2) of the EU pursuant to its powers under the royal prerogative to withdraw from international treaties. The Supreme Court has held that notice under Article 50 must be authorised by an Act of Parliament. This will require a bill to be passed before both Houses of Parliament, although the Court has made clear that a "very brief statute" would suffice: what matters is not the length or complexity of the statute but rather the fact that it will be primary legislation enacted by the Queen in Parliament. In light of this, attention may now turn to Ireland where a judicial review, aimed at establishing that notice under article 50 can be withdrawn, is about to be launched.

The issue before the Supreme Court and the arguments

As the Supreme Court has made clear throughout this process, and as it reiterated, the question before the court concerned the steps required as a matter of UK domestic law before the process of leaving the European Union can be initiated pursuant to Article 50. Article 50(1) says, "Any member state may decide to withdraw from the Union in accordance with its own constitutional requirements." The Supreme Court judgment specifies what those requirements are.

The primary argument of the claimants, which was accepted by the majority, was summarised by Lord Neuberger at paragraph 36 of the Judgment:

"36. The applicants' case in that connection is that when Notice is given, the United Kingdom will have embarked on an irreversible course that will lead to much of EU law ceasing to have effect in the United Kingdom, whether or not Parliament repeals the 1972 Act. As Lord Pannick QC put it for Mrs Miller, when ministers give Notice they will be "pulling ... the trigger which causes the bullet to be fired, with the consequence that the bullet will hit the target and the Treaties will cease to apply". In particular, he said, some of the legal rights which the applicants enjoy under EU law will come to an end. This, he submitted, means that the giving of Notice would pre-empt the decision of Parliament on the Great Repeal Bill. It would be tantamount to altering the law by ministerial action, or executive decision, without prior legislation, and that would not be in accordance with our law."

In other words, rights were granted by Parliament through EU membership and they were therefore Parliament's rights to take away, so the argument went.

The Government did not dispute that significant changes would follow from withdrawing from the EU Treaties but argued that this did not prevent the Government giving notice because the 1972 Act had not excluded the prerogative power to withdraw from treaties and that the 1972 Act gave effect to EU law only insofar as the EU Treaties required it.

The judgment of the majority

The judgment of the majority was given by the President of the Supreme Court, Lord Neuberger. Lord Neuberger examined the history of the UK's involvement with the EU. As one would have expected, the various European Treaties, such as the Treaties of Maastricht, Amsterdam, Nice and Lisbon, had all been ratified by Parliament. The UK legislation ratifying these Treaties had often stated that further changes should not be ratified "unless approved by an Act of Parliament" or imposed restrictions relating to amendments to the EU Treaty, including approval by an Act of Parliament (see paragraphs 24-30).

(i) The European Communities Act 1972

Lord Neuberger explained the constitutional significance of the 1972 Act, which was, in constitutional terms, unprecedented because it not only made EU law a source of UK law, but actually takes precedence over UK law, including Acts of Parliament. However, he emphasised that EU law only enjoyed this automatic and overriding effect by virtue of the 1972 Act and thus only while it remains in force and accepted that EU law would not apply if the UK ceased to be bound by the EU Treaties. But he held that (see paragraphs 77 and 78 of the Judgment):

"77. We also accept that Parliament cannot have intended that section 2 should continue to import the variable content of EU law into domestic law, or that the other consequences of the 1972 Act described in paras 62 to 64 above should continue to apply, after the United Kingdom had ceased to be bound by the EU Treaties. However, while acknowledging the force of Lord Reed's powerful judgment, we do not accept that it follows from this that the 1972 Act either contemplates or accommodates the abrogation of EU law upon the United Kingdom's withdrawal from the EU Treaties by prerogative act without prior Parliamentary authorisation. On the contrary: we consider that, by the 1972 Act, Parliament endorsed and gave effect to the United Kingdom's membership of what is now the European Union under the EU Treaties in a way which is inconsistent with the future exercise by ministers of any prerogative power to withdraw from such Treaties.

78. In short, the fact that EU law will no longer be part of UK domestic law if the United Kingdom withdraws from the EU Treaties does not mean that Parliament contemplated or intended that ministers could cause the United Kingdom to withdraw from the EU Treaties without prior Parliamentary approval. There is a vital difference between changes in domestic law resulting from variations in the content of EU law arising from new EU legislation, and changes in domestic law resulting from withdrawal by the United Kingdom from the European Union. The former involves changes in EU law, which are then brought into domestic law through section 2 of the 1972 Act. The latter involves a unilateral action by the relevant constitutional bodies which effects a fundamental change in the constitutional arrangements of the United Kingdom."

Lord Neuberger stressed that one of the most fundamental functions of the constitution of any state is to identify the sources of its law. As stated above, the 1972 Act was of such constitutional significance because it was the "conduit pipe" by which EU law was brought into UK domestic law as an overriding source of law. Lord Neuberger did not consider that the Government's arguments answered the objections based on the constitutional implications of withdrawal from the EU, which is fundamentally different from varying the content of EU law. Withdrawal, he said "will constitute as significant a constitutional change as that which occurred when EU law was first incorporated in domestic law by the 1972 Act." He said (at paragraph 81):

"It would be inconsistent with long-standing and fundamental principle for such a far-reaching change to the UK constitutional arrangements to be brought about by ministerial decision or ministerial action alone. All the more so when the source in question was brought into existence by Parliament through primary legislation, which gave that source an overriding supremacy in the hierarchy of domestic law sources."

Lord Neuberger accepted that parliament could have provided that the rights introduced under the 1972 Act would only prevail only for so long as the UK Government did not decide otherwise but he did not accept that the 1972 Act did so. Given that the 1972 Act required ministers not to commit to any new arrangement, whether it increased or decreased the potential volume and extent of EU law, without first obtaining Parliamentary approval, it would hardly have been compatible with these provisions if ministers, in reliance on prerogative powers, could unilaterally withdraw from the EU Treaties without Parliamentary approval. Indeed, it was also pointed out that if the Government's argument was right, they could have withdrawn from the EU even if there had not been a referendum or, in theory at least, even if there had been a vote to remain, which Lord Neuberger described as "implausible propositions".

Lord Neuberger also dismissed the arguments that a decision to withdraw using the prerogative powers would be acceptable because the decision could be subject to judicial review or because ministers were accountable to Parliament, pointing out that these arguments could be used to justify all sorts of powers being granted to ministers. Nor did he place any significance on the fact that Parliament will be formally involved in the process of withdrawal. Whilst accepting that this seemed likely, he considered that it missed the point because the die would be cast before Parliament became involved.

(ii) The Referendum Act 2015

As regards the Referendum Act 2015, the claimants argued that it had no legal significance, only political significance, because it did not specify the consequences that would follow from a vote to leave. The Government argued that the 2015 Act was enacted on the basis that the result of the referendum would be decisive and that, having referred the question whether to leave the EU to the electorate, Parliament cannot have intended that the same question would then be referred straight back to it.

Lord Neuberger rejected the Government's argument, considering that it assumed what it sought to prove, namely that the referendum was intended to have legal effect. The 2015 Act did not specify the consequences of a vote to leave and, as Lord Neuberger stated (at paragraph 121):

"121. Where, as in this case, implementation of a referendum result requires a change in the law of the land, and statute has not provided for that change, the change in the law must be made in the only way in which the UK constitution permits, namely through Parliamentary legislation."

Lord Neuberger acknowledged that the result of the referendum did not have any legal effect but did recognise its great political significance.

"124. Thus, the referendum of 2016 did not change the law in a way which would allow ministers to withdraw the United Kingdom from the European Union without legislation. But that in no way means that it is devoid of effect. It means that, unless and until acted on by Parliament, its force is political rather than legal. It has already shown itself to be of great political significance."

(iii) The form of legislation required

The Supreme Court considered the question of the form of legislation required to trigger Article 50 to be "entirely a matter for Parliament" but, having said that, Lord Neuberger did make clear that a very brief statute would suffice:

"122. What form such legislation should take is entirely a matter for Parliament. But, in the light of a point made in oral argument, it is right to add that the fact that Parliament may decide to content itself with a very brief statute is nothing to the point. There is no equivalence between the constitutional importance of a statute, or any other document, and its length or complexity. A notice under article 50(2) could no doubt be very short indeed, but that would not undermine its momentous significance. The essential point is that, if, as we consider, what would otherwise be a prerogative act would result in a change in domestic law, the act can only lawfully be carried out with the sanction of primary legislation enacted by the Queen in Parliament."

(iv) Devolution questions

The case before the Supreme Court also raised issues regarding the effect of devolution for Scotland and Northern Ireland and whether the approval of their respective Parliaments to the UK's withdrawal from the EU was required. The Supreme Court unanimously held that such approval was not required.

Although there is a political convention, known as the Sewel Convention and now embodied in a Memorandum of Understanding, which states that:

"The UK Government will proceed in accordance with the convention that the UK Parliament would not normally legislate with regard to devolved matters except with the agreement of the devolved legislature. The devolved administrations will be responsible for seeking such agreement as may be required for this purpose on an approach from the UK Government."

However, the Memorandum also made clear that this was just a statement of political intent and that it did not create legal obligations.

Lord Neuberger observed that "Judges ... are neither the parents nor the guardians of political conventions; they are merely observers" and as such the court did not have jurisdiction to enforce it.

The dissenting judgments

Three of the eleven justices dissented: Lords Reed, Carnwath and Hughes. The main dissenting judgment was given by Lord Reed.

Lord Reed accepted the importance in the UK's constitutional law of the principle of Parliamentary sovereignty over domestic law but did not consider that Parliament had to enact an Act of Parliament before the UK can leave the EU. This is because he considered the effect which Parliament has given to EU to be conditional on the application of the EU Treaties to the UK and therefore on the UK's membership of the EU.

Lord Reed did not consider the 1972 Act to impose any requirement, or to manifest any intention, in respect of the UK's membership of the EU and did not therefore affect the Crown's exercise of prerogative powers in respect of foreign relations, including the power to enter into or withdraw from international treaties (see paragraphs 177). Lord Reed considered that this fundamental provision could only be overridden by express or necessary provision.

Lord Reed also considered the effect of the Referendum Act 2015 and was of the view that as Parliament had not given itself a further role in the process, as it had done in respect of other Acts relation to the EU where it had required Parliamentary approval of certain decisions, it was hard to regard such a requirement as being implicit.

Lord Reed also accepted the Government's argument that the 1972 Act gave effect in domestic law to a body of law known as EU law, which could alter from time to time, and that this could include the repeal and restriction of EU rights previously created (see paragraph 216). In his view, the 1972 Act "simply creates a scheme under which domestic law reflects the UK's international obligations, whatever they may be." (see paragraph 217). He did not accept that notice under article 50 would alter the law of the land and considered that in any event Parliament could legislate so as to protect rights. But equally it had to be accepted that Parliament could not recreate certain EU law rights, which only served to emphasise the different nature of EU law.

Lord Hughes agreed with Lord Reed's judgment. Lord Carnwath also agreed with Lord Reed but explained his reasoning in more detail. He considered it illogical to search in the 1972 Act for a presumed Parliamentary intention in respect of withdrawal at a time when the Treaty contained no express power to withdraw and there was no reason for Parliament to consider it (during the hearing an analogy was drawn with a bride on her wedding day who will usually not be considering divorce!). Article 50 was introduced by the Treaty of Lisbon and the 2008 Act which recognised that the treaty did not impose any restriction on the exercise of Article 50 by the Executive. A 2011 Act made reference to Article 50(3) but did not refer to Article 50(2). He therefore did not consider that the 1972 Act or subsequent legislation removes the Crown's treaty-making prerogative.

Lord Carnwath agreed with Maguire J in the Northern Ireland proceedings, who said a distinction should be drawn between what occurs on the triggering of Article 50(2) and what may occur thereafter. Lord Carnwath considered the trigger/bullet analogy used by Lord Pannick QC for the claimants to be fallacious:

"262. Lord Pannick's trigger/bullet analogy is superficially attractive, but (with respect) fallacious. A real bullet does not take two years to reach its target. Nor is its progress accompanied by an intense period of negotiations over the form of protection that should be available to the victim by the time it arrives. The treaties will indeed cease to apply, and domestic law will change; but it is clearly envisaged that the final form of the changes will be governed by legislation. As the Secretary of State has explained, the intention is that the legislation will where possible reproduce existing European-based rights in domestic law, but otherwise ensure that there is no legal gap."

Lord Carnwath noted the unprecedented and enormous nature of the legal and practical changes caused by Brexit and that the Article 50 process "must and will involve a partnership between Parliament and the Executive". But he did not consider that this means that legislation is required simply to initiate it. Legislation will undoubtedly be required to implement withdrawal, but the process, including the form and timing of any legislation, can and should be determined by Parliament and not by the courts.


The decision of the Supreme Court does not come as a surprise, save perhaps that there were as many as three dissenting judgments. It had been widely reported that the Government was expecting defeat and had prepared various forms of legislation to put before Parliament in order to start the legislative process in the hope of meeting the Prime Minister's self-imposed deadline for issuing notice under article 50 by the end of March 2017.

What is most interesting though is that the case proceeded on the basis that notice under article 50(2) cannot be given in qualified or conditional terms and that, once given, it cannot be withdrawn (see paragraph 26 of the judgment). This was common ground between the parties. The Government's case was that even if this common ground was mistaken, it made no difference to the outcome of the case. From a purely legal perspective, this a surprising concession to have made; if a notice under article 50(2) can be withdrawn then it is far from inevitable that the rights will be taken away.

Politically though it is more understandable. The Prime Minister has been quite clear that "Brexit means Brexit" and has refused to entertain the prospect of there being a further referendum to see if the UK really does want to leave. However, the EU Treaty does not make clear whether a notice is revocable, but there are many who argue that it is. Indeed, it is understood that there is to be a judicial review in the Republic of Ireland, organised by an English QC and financed through crowdfunding, the aim of which is to establish that notice under Article 50 is revocable and can be withdrawn and therefore to pave the way for a further referendum before the UK leaves the EU. Unlike the question before the Supreme Court though, the question of the revocability of notice would be a question of the interpretation of the EU Treaty, which is ultimately for the Court of Justice of the European Union to determine. This may also have been a factor in the Government's decision not to touch the revocability issue as it would almost certainly have resulted in the question being referred to the European Court. This would not have gone down well with those who wished to leave and for many of whom the notion of "justice" being dispensed from a court sat in Luxembourg was distinctly unpalatable.

It seems likely that Parliament will pass an Act approving a notice under Article 50, although it remains to be seen how much opposition there is in both Houses. Once notice is served, that will start the two-year period for negotiations between the UK and rest of the EU as to the terms of departure and any replacement treaty.

Those who wish to remain may wish to turn their attention to what is happening in Ireland. There are many, such as former Prime Minister, Tony Blair, and former deputy prime Minister, Nick Clegg, who consider the referendum to be part of an ongoing dialogue and who think that a further referendum should not be ruled out. If, once negotiations have started, the UK does not look likely to achieve a satisfactory exit deal the calls for a second referendum may become louder.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.

To print this article, all you need is to be registered on

Click to Login as an existing user or Register so you can print this article.

In association with
Related Video
Up-coming Events Search
Font Size:
Mondaq on Twitter
Register for Access and our Free Biweekly Alert for
This service is completely free. Access 250,000 archived articles from 100+ countries and get a personalised email twice a week covering developments (and yes, our lawyers like to think you’ve read our Disclaimer).
Email Address
Company Name
Confirm Password
Mondaq Topics -- Select your Interests
 Law Performance
 Law Practice
 Media & IT
 Real Estate
 Wealth Mgt
Asia Pacific
European Union
Latin America
Middle East
United States
Worldwide Updates
Mondaq Ltd requires you to register and provide information that personally identifies you, including what sort of information you are interested in, for three primary purposes:
  • To allow you to personalize the Mondaq websites you are visiting.
  • To enable features such as password reminder, newsletter alerts, email a colleague, and linking from Mondaq (and its affiliate sites) to your website.
  • To produce demographic feedback for our information providers who provide information free for your use.
  • Mondaq (and its affiliate sites) do not sell or provide your details to third parties other than information providers. The reason we provide our information providers with this information is so that they can measure the response their articles are receiving and provide you with information about their products and services.
    If you do not want us to provide your name and email address you may opt out by clicking here
    If you do not wish to receive any future announcements of products and services offered by Mondaq you may opt out by clicking here

    Terms & Conditions and Privacy Statement (the Website) is owned and managed by Mondaq Ltd and as a user you are granted a non-exclusive, revocable license to access the Website under its terms and conditions of use. Your use of the Website constitutes your agreement to the following terms and conditions of use. Mondaq Ltd may terminate your use of the Website if you are in breach of these terms and conditions or if Mondaq Ltd decides to terminate your license of use for whatever reason.

    Use of

    You may use the Website but are required to register as a user if you wish to read the full text of the content and articles available (the Content). You may not modify, publish, transmit, transfer or sell, reproduce, create derivative works from, distribute, perform, link, display, or in any way exploit any of the Content, in whole or in part, except as expressly permitted in these terms & conditions or with the prior written consent of Mondaq Ltd. You may not use electronic or other means to extract details or information about’s content, users or contributors in order to offer them any services or products which compete directly or indirectly with Mondaq Ltd’s services and products.


    Mondaq Ltd and/or its respective suppliers make no representations about the suitability of the information contained in the documents and related graphics published on this server for any purpose. All such documents and related graphics are provided "as is" without warranty of any kind. Mondaq Ltd and/or its respective suppliers hereby disclaim all warranties and conditions with regard to this information, including all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement. In no event shall Mondaq Ltd and/or its respective suppliers be liable for any special, indirect or consequential damages or any damages whatsoever resulting from loss of use, data or profits, whether in an action of contract, negligence or other tortious action, arising out of or in connection with the use or performance of information available from this server.

    The documents and related graphics published on this server could include technical inaccuracies or typographical errors. Changes are periodically added to the information herein. Mondaq Ltd and/or its respective suppliers may make improvements and/or changes in the product(s) and/or the program(s) described herein at any time.


    Mondaq Ltd requires you to register and provide information that personally identifies you, including what sort of information you are interested in, for three primary purposes:

    • To allow you to personalize the Mondaq websites you are visiting.
    • To enable features such as password reminder, newsletter alerts, email a colleague, and linking from Mondaq (and its affiliate sites) to your website.
    • To produce demographic feedback for our information providers who provide information free for your use.

    Mondaq (and its affiliate sites) do not sell or provide your details to third parties other than information providers. The reason we provide our information providers with this information is so that they can measure the response their articles are receiving and provide you with information about their products and services.

    Information Collection and Use

    We require site users to register with Mondaq (and its affiliate sites) to view the free information on the site. We also collect information from our users at several different points on the websites: this is so that we can customise the sites according to individual usage, provide 'session-aware' functionality, and ensure that content is acquired and developed appropriately. This gives us an overall picture of our user profiles, which in turn shows to our Editorial Contributors the type of person they are reaching by posting articles on Mondaq (and its affiliate sites) – meaning more free content for registered users.

    We are only able to provide the material on the Mondaq (and its affiliate sites) site free to site visitors because we can pass on information about the pages that users are viewing and the personal information users provide to us (e.g. email addresses) to reputable contributing firms such as law firms who author those pages. We do not sell or rent information to anyone else other than the authors of those pages, who may change from time to time. Should you wish us not to disclose your details to any of these parties, please tick the box above or tick the box marked "Opt out of Registration Information Disclosure" on the Your Profile page. We and our author organisations may only contact you via email or other means if you allow us to do so. Users can opt out of contact when they register on the site, or send an email to with “no disclosure” in the subject heading

    Mondaq News Alerts

    In order to receive Mondaq News Alerts, users have to complete a separate registration form. This is a personalised service where users choose regions and topics of interest and we send it only to those users who have requested it. Users can stop receiving these Alerts by going to the Mondaq News Alerts page and deselecting all interest areas. In the same way users can amend their personal preferences to add or remove subject areas.


    A cookie is a small text file written to a user’s hard drive that contains an identifying user number. The cookies do not contain any personal information about users. We use the cookie so users do not have to log in every time they use the service and the cookie will automatically expire if you do not visit the Mondaq website (or its affiliate sites) for 12 months. We also use the cookie to personalise a user's experience of the site (for example to show information specific to a user's region). As the Mondaq sites are fully personalised and cookies are essential to its core technology the site will function unpredictably with browsers that do not support cookies - or where cookies are disabled (in these circumstances we advise you to attempt to locate the information you require elsewhere on the web). However if you are concerned about the presence of a Mondaq cookie on your machine you can also choose to expire the cookie immediately (remove it) by selecting the 'Log Off' menu option as the last thing you do when you use the site.

    Some of our business partners may use cookies on our site (for example, advertisers). However, we have no access to or control over these cookies and we are not aware of any at present that do so.

    Log Files

    We use IP addresses to analyse trends, administer the site, track movement, and gather broad demographic information for aggregate use. IP addresses are not linked to personally identifiable information.


    This web site contains links to other sites. Please be aware that Mondaq (or its affiliate sites) are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of these third party sites. This privacy statement applies solely to information collected by this Web site.

    Surveys & Contests

    From time-to-time our site requests information from users via surveys or contests. Participation in these surveys or contests is completely voluntary and the user therefore has a choice whether or not to disclose any information requested. Information requested may include contact information (such as name and delivery address), and demographic information (such as postcode, age level). Contact information will be used to notify the winners and award prizes. Survey information will be used for purposes of monitoring or improving the functionality of the site.


    If a user elects to use our referral service for informing a friend about our site, we ask them for the friend’s name and email address. Mondaq stores this information and may contact the friend to invite them to register with Mondaq, but they will not be contacted more than once. The friend may contact Mondaq to request the removal of this information from our database.


    From time to time Mondaq may send you emails promoting Mondaq services including new services. You may opt out of receiving such emails by clicking below.

    *** If you do not wish to receive any future announcements of services offered by Mondaq you may opt out by clicking here .


    This website takes every reasonable precaution to protect our users’ information. When users submit sensitive information via the website, your information is protected using firewalls and other security technology. If you have any questions about the security at our website, you can send an email to

    Correcting/Updating Personal Information

    If a user’s personally identifiable information changes (such as postcode), or if a user no longer desires our service, we will endeavour to provide a way to correct, update or remove that user’s personal data provided to us. This can usually be done at the “Your Profile” page or by sending an email to

    Notification of Changes

    If we decide to change our Terms & Conditions or Privacy Policy, we will post those changes on our site so our users are always aware of what information we collect, how we use it, and under what circumstances, if any, we disclose it. If at any point we decide to use personally identifiable information in a manner different from that stated at the time it was collected, we will notify users by way of an email. Users will have a choice as to whether or not we use their information in this different manner. We will use information in accordance with the privacy policy under which the information was collected.

    How to contact Mondaq

    You can contact us with comments or queries at

    If for some reason you believe Mondaq Ltd. has not adhered to these principles, please notify us by e-mail at and we will use commercially reasonable efforts to determine and correct the problem promptly.

    By clicking Register you state you have read and agree to our Terms and Conditions