The House of Lords Constitution Committee today publishes its report on the process by which the United Kingdom will withdraw from the European Union, a process that will result “in the most significant changes to the UK’s constitution in a generation”. The Committee accepts that the referendum result is clear and therefore must be implemented, but it is also firmly of the view that Parliament must be involved: “The Government should not trigger Article 50 [TEU] without consulting Parliament.”

Parliament, the Executive and Article 50

Turning to Article 50, the Committee accepts that the process it sets out offers the only “viable” route by which withdrawal can be effected. It then addresses whether a notification under this provision might later be revoked unilaterally by the United Kingdom. The Committee considers the legal position to be unclear but notes that, should any attempt to do so by the UK be disputed by another member state, the matter would be decided by the Court of Justice. On this basis, and given that the uncertainty would only ever be resolved after Article 50 had already been triggered, the Committee deems it prudent for Parliament to work on the assumption that the triggering of Article 50 is an action that the UK cannot unilaterally reverse.

Article 50 of course leaves discretion to any Member State to decide to withdraw from the Union “in accordance with its own constitutional requirements.” The Committee observes that neither the question put to the electorate nor the provisions of the European Union Referendum Act 2015 set out how or when withdrawal should take place. Accordingly, the focus of most of the report is upon the respective roles and responsibilities of both Government and Parliament in managing the withdrawal process.

The issues surrounding the triggering of Article 50, and the appropriate role for Parliament in this process, will of course be aired before the High Court in October. In those proceedings, it will be argued that triggering Article 50 will lead inevitably to the repeal of the European Communities Act 1972, thereby affecting citizens’ statutory rights incorporated thereby. These impending consequences, it is argued, prevent the UK Government from activating Article 50 by way of the royal prerogative, requiring instead statutory authorisation by Parliament. The Government, on the other hand, maintains that it can invoke Article 50 as an act of the prerogative, and that “there is no legal obligation to consult Parliament on triggering Article 50” (HL Deb, 18 July 2016, col 430 [Lords Chamber]). Since the issue is subject to live proceedings, the Committee opts not to express a view on the differing legal arguments. Instead it focuses upon whether, and if so how, it would be constitutionally appropriate for Parliament to be involved, irrespective of whether or not the courts decide that statutory authority for triggering Article 50 is a legal requirement.

To this end, Parliament should play a “central role” not only in the decision to trigger Article 50 but also during the negotiation process itself and at the point where the negotiated package is agreed and adopted. The Committee also anticipates that this role should continue, with parliamentary scrutiny of any ongoing relationship between the United Kingdom and the EU. Significantly, the Committee asserts that it is for Parliament itself to determine how it will be involved at each of these stages in the withdrawal process.

The nature and degree of Parliament’s involvement

The Report proceeds to consider two matters concerning Parliament’s involvement—namely, whether that involvement should take the form of the enactment of legislation or the passing of a resolution, and the scope of the matters that ought to be addressed by any such legislation or resolution.

As to the first matter, the Committee notes that the two mechanisms each have their own attractions and drawbacks. A resolution would be capable of being adopted more swiftly than legislation could be enacted, and would therefore enable Parliament rapidly to set out its position. The Committee sees a strong case for resolutions of both Houses (rather than just of the Commons) but notes the risk of differently worded motions being passed.

Legislation, the Committee notes, would entail different risks (as well as opportunities). Legislating would likely take longer, and doing so might invite complications so far as the territorial constitution is concerned, given the possibility of devolved legislatures choosing to vote on legislative consent motions in relation to any Bill. That said, the Committee takes the view that the Sewel Convention would not actually apply: triggering Article 50, it says, would not engage devolved matters or affect the scope of devolved competence—and, in any event, legislating to give effect to the referendum outcome could be considered to amount to circumstances that are not “normal” within the meaning of the Convention.

The Report also highlights certain attractions of legislation—two in particular. In the first place, the Committee notes that while a resolution could be used to signal Parliament’s assent to the triggering of Article 50, only legislation could place beyond doubt any questions about where authority lies to pull the trigger. Second, the Committee notes that any legislation enacted on this matter would become part of the UK’s “constitutional requirements” for the purpose of Article 50. In this way, the Committee suggests, Parliament could leverage existing uncertainty concerning the existence and content of such requirements by choosing legislatively to prescribe them. In doing so, Parliament could “take control of the process by which Article 50 was to be triggered”. For instance: “an Act could state that Parliament authorised the UK Government to trigger Article 50 if—and only if—the Government had first presented for parliamentary approval its proposal for the UK’s new relationship with the EU on the basis of which it intended to negotiate.”

The Committee ultimately does not come down decisively on the side of either a resolution or legislation, instead emphasising that what is crucial is that the use of one or other of those mechanisms enables Parliament to play an appropriate constitutional role in the triggering of Article 50. As to the scope of any resolution or legislation, the Committee notes that Parliament will need to decide whether to focus simply upon the triggering of Article 50 or to set out a more detailed “route map” as to its involvement throughout the Brexit process. A resolution or Bill might, for instance, require Ministers to report to Parliament at various stages in the negotiation process; set out the extent and form of any parliamentary involvement in that process; and determine at what stages, if any, Parliament’s consent to the continuation of negotiations should be required. In deciding whether such details should be included in a resolution or Bill, the Committee observes that a balance will have to be struck between “the benefits of parliamentary involvement in the negotiation process” and a degree of over-prescriptiveness that would risk “hobbling the Government’s ability to negotiate”.

Concluding remarks

The Report offers broader reflections about the future use of referendums in the United Kingdom, as well as the interplay between prerogative powers in the area of foreign affairs on the one hand, and constitutional conventions on the other.

It is of course possible for the UK Parliament to provide that a referendum is to have a legally binding outcome; the referendum held in 2011 on the use of the Alternative Vote is an example. It can be argued that the 2015 Act should have been more detailed in setting out what would happen in the event of a Leave vote, and in particular what the respective roles for Government and Parliament ought to be in the process that would flow from it. On this basis the Committee recommends that Parliament may wish, in future, “to ensure that detailed consideration is given to how the result of a 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.”

The Committee also draws an analogy between triggering Article 50 and the prerogative power to go to war or to deploy the UK’s armed forces. The Committee, in a report published in 2013, took the view that there is 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” (para 64). While it accepts that no convention has formed to govern how Parliament should be involved in enacting and ratifying the result of a referendum, the Committee considers there to be 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.” The Committee therefore avers that it would be “constitutionally unacceptable, not to mention setting a disturbing precedent, for the Government to act on an advisory referendum without explicit parliamentary approval—particularly one with such significant long-term consequences”.

Triggering the Article 50 process is, in itself, of huge significance, heralding as it does the United Kingdom’s withdrawal from a treaty system within which it has been closely integrated for over forty years, and which has exerted profound and far-reaching influences upon both the UK’s constitution and the daily lives of its citizens. But the controversy that is now playing out in respect of Article 50—and the broader associated questions concerning how and by whom Brexit should be taken forward—also highlights the tensions that exist within our unwritten system over the respective roles for the public, the executive and the legislature in both initiating and giving effect to constitutional change.

In what is still—judged by reference to the timescale over which Brexit is likely to play out—the immediate aftermath of the referendum, it may seem inapposite to focus upon how future major constitutional changes should be managed. But for two reasons, the opposite is true. For one thing, the UK will inevitably have to confront further significant—and perhaps even existential—questions about its constitutional future. Learning from the experience, and arguably the mistakes, of Brexit would be prudent; failing to do so would be, at best, negligent. Second, the referendum might, for many, have felt like the end—and it certainly did mark at least the beginning of the end of the UK’s current constitutional position vis-à-vis the EU. However, just as devolution was famously said to be a “process not an event”, it is also the case that Brexit—and the questions to which it gives rise about the UK’s new relationship with the EU—is likely to be an issue that runs and runs. For that reason, it is crucial that clarity be brought to bear upon where constitutional responsibility lies not merely for triggering Article 50 but in respect of the lengthy and vastly complicated process of negotiation and legal and constitutional change that will follow in the wake of Article 50’s activation. That Parliament should play a major role in that process is a strongly defensible if ultimately contestable argument. But the proposition that as the Brexit process begins in earnest there should at the very least be certainty in this area—whatever division of responsibility is ultimately settled upon—is surely incontrovertible.

Mark Elliott is Professor of Public Law at the University of Cambridge. Stephen Tierney is Professor of Constitutional Theory at the University of Edinburgh. They both serve as Legal Advisers to the House of Lords Constitution Committee. They have written this post in purely personal capacities.