5.The 23 June referendum demonstrated the electorate’s desire for the UK to withdraw from the European Union: 33,577,342 people voted in the referendum, of whom 17.4 million people (51.9 per cent) voted to leave and 16.1 million (48.1 per cent) voted to remain in the EU. Yet neither the question put to the electorate, nor the provisions of the Act under which the referendum took place, set out how or when withdrawal should take place in the event of a vote to leave. The absence of any prior provision for implementing the referendum result means that questions of how and when the process of withdrawal from the EU should proceed have become matters of significant national debate.
6.The referendum result was clear. It will be the Government’s task to determine how the will of the people, expressed in binary terms in the referendum, should be implemented, and where among the range of potential outcomes the final settlement by which the UK leaves the EU will be made.
7.Article 50 of the Treaty on European Union sets out how member states may withdraw from the European Union. It states that “Any Member State may decide to withdraw from the Union in accordance with its own constitutional requirements.”
8.The UK Government, in its Command Paper The process for withdrawing from the European Union, stated that “The rules for exit are set out in Article 50 of the Treaty on European Union. This is the only lawful route available to withdraw from the EU.” Suggestions have been made that the UK could leave the EU by simply repealing the European Communities Act 1972. The Command Paper dismissed this proposal, noting that:
“It would be a breach of international and EU law to withdraw unilaterally from the EU (for example, by simply repealing the domestic legislation that gives the EU law effect in the UK). Such a breach would create a hostile environment in which to negotiate either a new relationship with the remaining EU member states, or new trade agreements with non-EU countries.”
9.In its report, The process of withdrawing from the European Union, the House of Lords European Union Committee concurred: “If a member state decides to withdraw from the EU, the process described in Article 50 is the only way of doing so consistent with EU and international law.” We agree with the position taken by the UK Government and the Lords European Union Committee that Article 50 is the only viable route for the UK to withdraw from the European Union.
10.Article 50 goes on to state how withdrawal will be triggered: “A member state which decides to withdraw shall notify the European Council of its intention.” When the UK notifies the European Council of its intention to withdraw from the EU, a two year period commences in which arrangements must be negotiated for the UK’s withdrawal. Those arrangements must be agreed by the European Council, acting by qualified majority, and after obtaining the consent of the European Parliament. If no agreement is reached, the UK ceases to be a member of the EU at the end of the two year period unless all the member states of the EU (including the UK) agree to an extension. The triggering of Article 50 is crucial. Whilst it is only one stage in a complicated and lengthy process, it is the moment at which the countdown starts and an initial deadline for the UK’s withdrawal from the EU is set.
11.It is unclear whether the UK could, after triggering Article 50, unilaterally choose to withdraw its notification of withdrawal from the EU (thereby stopping the two year countdown to withdrawal). The House of Lords European Union Committee concluded in 2015 that “There is nothing in Article 50 formally to prevent a Member State from reversing its decision to withdraw in the course of the withdrawal negotiations. The political consequences of such a change of mind would, though, be substantial.” Others argue that once triggered, Article 50 may not be unilaterally revoked by the member state concerned, although it could be reversed by the unanimous agreement of all EU member states.
12.Participants at our seminar were also divided on this point. As one noted, “there is nothing in Article 50 itself one way or another; it does not say that you can retract or, once invoked, that you cannot retract. So it is left to the lawyers to have those enjoyable disputes to sort it out.” Should any attempt by the UK to unilaterally withdraw its notification under Article 50 be disputed by another member state, the matter would be decided by the European Court of Justice.
13.It is unclear whether a notification under Article 50, once made, could be unilaterally withdrawn by the UK without the consent of other EU member states. In the light of the uncertainty that exists on this point, and given that the uncertainty would only ever be resolved after Article 50 had already been triggered, we consider that it would be prudent for Parliament to work on the assumption that the triggering of Article 50 is an action that the UK cannot unilaterally reverse.
14.Given the uncodified nature of the UK’s constitution, it is not entirely clear what the UK’s “constitutional requirements” are for the purposes of Article 50. The Government’s position is that it can invoke Article 50 as an act of royal prerogative, and that “there is no legal obligation to consult Parliament on triggering Article 50”. Lord Keen of Elie QC, the Advocate General for Scotland, stated in the House of Lords that “the Executive has certain prerogative powers that it exercises in international legal matters, including the making and unmaking of treaties. That remains the position.”
15.Others have argued that, as a matter of domestic law, the Government is unable to trigger Article 50 without the consent of Parliament. A number of different reasons have been given for this. They include:
16.A legal challenge has been made to the Government’s position that it may trigger Article 50 as an exercise of prerogative power. A full hearing at the High Court is expected to take place in October 2016. We do not intend therefore to express a view as to the merits or otherwise of the differing legal arguments set out above. Rather we consider whether, and if so how, it would be constitutionally appropriate for Parliament to be involved, irrespective of whether the courts decide that parliamentary involvement is a legal requirement.
17.Parliamentary sovereignty is a core principle of the UK constitution. The referendum enabled the will of the UK people to be expressed, but it was, in strict legal terms, an advisory referendum only. As we observed in our 2010 report on referendums, Parliament can provide, in the legislation enabling a referendum, that a referendum result will automatically bring about certain legal consequences (although, being sovereign, Parliament can later amend or repeal such a provision), or it can expressly instruct the Government to bring forward legislation to implement the result. The 2016 referendum on membership of the EU does not technically fall into either category: the European Union Referendum Act 2015 contains no provision legally requiring the Government to act in a specific way, nor does it explicitly provide that the result is binding.
18.The legislation that enabled the EU referendum did not set out how the result would be implemented. This has caused uncertainty and confusion in the aftermath of the referendum, particularly given the uncertainty over whether statutory authorisation is now required to trigger Article 50. Parliament may wish, in future, to ensure that detailed consideration is given to how the result of any referendum will be implemented in advance of the vote itself occurring, and to whether explicit provision should be made in the enabling legislation either to implement the outcome automatically or to instruct the Government to act on the result.
19.Although the referendum was not legally binding, it was accompanied and preceded by clear political commitments from the UK Government to act on the referendum result. Indeed, the referendum was the result of a general election manifesto commitment by the Conservative Party which stated that “We will honour the result of the referendum, whatever the outcome”. Given that commitment, the question that follows is what role Parliament should play in taking forward that result.
20.One participant argued at our seminar that: “Parliament has not approved leaving the EU; we have simply gone towards a pure ‘direct democracy’ view of how the decision might be taken, which is a very big shift away from our traditional constitution.” Parliament should not, they told us, be excluded from the process by which the UK leaves the EU simply because that course of action was decided by a referendum. Another stated that, “Even if it is a Royal Prerogative issue, the convention seems to me to be crystal clear, and that is, that you cannot make a major treaty change without getting Parliament’s prior approval, particularly when it has a clear knock-on consequence on domestic law that will follow on it.”
21.One analogy often cited at our seminar and by other commentators is the use of the royal prerogative power to go to war, or to deploy the UK’s armed forces. We explored the issues around this prerogative power in two inquiries in 2006 and 2013 and concluded that there was now a convention that “save in exceptional circumstances, the House of Commons is given the opportunity to debate and vote on the deployment of armed force overseas”. We added that:
“The Government have recognised that the need for Commons approval of deployment decisions is now a constitutional convention, and therefore politically binding on them … The current arrangements are such that it is inconceivable that the Prime Minister would either refuse to allow a Commons debate and vote on a deployment decision, or would refuse to follow the view of the Commons as expressed by a vote.”
22.Referendums are rarely held in the United Kingdom. Referendums which have the potential to affect such a significant change in the UK’s constitution are rarer still. There has thus been no opportunity for a convention to have formed to govern how Parliament should be involved in enacting and ratifying the result of a referendum. Nonetheless, we consider that there is a strong argument that enacting the result of a referendum of this magnitude should require at least the same level of parliamentary involvement as a decision to authorise a military deployment.
23.In addition, we note that whatever agreement is reached, Parliament will have to legislate to implement the UK’s new relationship with the EU. It seems only appropriate that the Executive ensures it has proper parliamentary approval for a process that will, eventually, require legislation to implement.
24.It would be constitutionally inappropriate, not to mention setting a disturbing precedent, for the Executive to act on an advisory referendum without explicit parliamentary approval—particularly one with such significant long-term consequences. The Government should not trigger Article 50 without consulting Parliament.
25.Parliament and the Government should discuss and agree the role each will play in the withdrawal process as a whole. The formal withdrawal process can be broken down into three stages, and we consider that some form of parliamentary approval or oversight will be required for each. The first stage is the triggering of Article 50. As we note above (see paragraphs 11–13), once Article 50 is triggered an initial deadline for the UK’s withdrawal from the EU is set and the UK should act on the assumption that it could no longer unilaterally affect the timetable for withdrawal. Getting the timing and circumstances of the start of the formal negotiation process right is therefore vitally important. It should not be rushed.
26.The second stage is the negotiation process itself, while the third stage will be the point at which the negotiated outcome is agreed and adopted. There may, in addition, be some elements of the UK’s on-going relationship with the EU which will require continued parliamentary scrutiny and oversight. The House of Lords European Union Committee recently published a report, Scrutinising Brexit: the role of Parliament, which addressed some of the questions as to how Parliament should be involved in the negotiation process, focusing in particular on the second of these stages. We consider that thought should also be given at an early stage as to how the negotiated withdrawal package will be agreed and implemented by Parliament.
27.In our representative democracy, it is constitutionally appropriate that Parliament should take the decision to act following the referendum. This means that Parliament should play a central role in the decision to trigger the Article 50 process, in the subsequent negotiation process, and in approving or otherwise the final terms under which the UK leaves the EU.
28.In this report we focus mainly on the manner in which Parliament should approve the triggering of Article 50. Yet the issue of parliamentary involvement in the negotiation process as a whole must also be tackled sooner rather than later. In Chapter 4 of this report we set out some of the issues that Parliament may wish to consider should it choose to address Parliament’s wider role in the negotiation process at the same time as considering the narrower issue of the triggering of Article 50.
1 Electoral Commission, ‘EU referendum results’: [accessed 8 September 2016]. The turnout was 72.2% of eligible electors.
3 , Treaty on European Union.
4 Foreign and Commonwealth Office, The process for withdrawing from the European Union, Cm 9216, February 2016, pp 7 and 13: [accessed 28 August 2016]
5 European Union Committee, , (11th Report, Session 2015–16, HL Paper 138), para 14.
6 European Union Committee, , para 15.
7 See, for example Jake Rylatt, ‘The Irrevocability of an Article 50 Notification: Lex Specialis and the Irrelevance of the Purported Customary Right to Unilaterally Revoke’ UK Constitutional Law Association Blog, 27 July 2016: [Accessed 30 August 2016]
8 Constitution Committee private seminar, July 2016
9 HL Deb, 18 July 2016,
10 HL Deb, 18 July 2016, . See also Mark Elliott, ‘Brexit: On why, as a matter of law, triggering Article 50 does not require Parliament to legislate’ Public Law for Everyone Blog, 30 June 2016: [Accessed 31 Aug 2016]; Kenneth Armstrong, ‘Push Me, Pull You: Whose Hand on the Article 50 Trigger?’ UK Constitutional Law Association Blog, 27 June 2016: [accessed 31 Aug 2016]
11 Nick Barber, Tom Hickman and Jeff King, ‘Pulling the Article 50 “Trigger”: Parliament’s Indispensable Role’, UK Constitutional Law Association Blog, 27 Jun 2016: [Accessed 30 Aug 2016]
12 John Adenitire, ‘The Executive Cannot Abrogate Fundamental Rights without Specific Parliamentary Mandate: The Implications of the EU Charter of Fundamental Rights for Triggering Art 50’, UK Constitutional Law Association Blog, 21 July 2016: [Accessed 30 Aug 2016]
13 T.T. Arvind, Richard Kirkham, and Lindsay Stirton, ‘Article 50 and the European Union Act 2011: Why Parliamentary Consent is Still Necessary’ UK Constitutional Law Association Blog, 1 July 2016: [Accessed 30 Aug 2016]
14 Constitution Committee, (12th Report, Session 2009–10; HL Paper 99) para 194.
15 Automatic implementation was, for example, set out in the which contained amendments to electoral law to introduce the Alternative Vote electoral system if its adoption was approved by in the May 2011 referendum. Meanwhile, of the Northern Ireland Act 1998 instructs the Government to act on the result of a referendum, stating that if a referendum result favours Northern Ireland becoming “part of a united Ireland, the Secretary of State shall lay before Parliament such proposals to give effect to that wish as may be agreed between Her Majesty’s Government in the United Kingdom and the Government of Ireland”.
16 See Speech by the Prime Minister on Europe at Chatham House, 10 November 2015: [Accessed 2 September 2016]
17 The Conservative Party, Conservative Manifesto 2015, p 73: [accessed 9 September 2016]
18 Constitution Committee private seminar, July 2016
20 Constitution Committee, (2nd Report, Session 2013–14; HL Paper 46) para 64. In the report, we rejected calls for legislation setting out the process of parliamentary approval. See also Constitution Committee, (15th Report, Session 2005–06; HL Paper 236)
21 Constitution Committee, , paras 63-63.
22 For ease of reference, we use the term ‘withdrawal process’ to cover both negotiations over the terms of the UK’s exit from the EU and the negotiation of the new relationship between the two, as identified by the Lords EU Committee. While they could take place consecutively, we consider them to be parts of a single withdrawal process.
23 European Union Committee, , (1st Report, Session 2016–17, HL Paper 33)