For the withdrawal process to begin, Article 50(1) of the Treaty of Lisbon requires a decision to leave the EU to have been made according to our own “constitutional requirements” (règles constitutionnelles in the less awkward French version of the text). So what counts as a decision to leave, and therefore as an event capable of triggering the withdrawal mechanisms in Article 50, is a question of domestic constitutional law. Three understandings of what would count as such a decision have attracted support in recent days. This post summarises those three positions before articulating and defending a fourth, hitherto neglected, possibility. I argue that the decision must be made under the statutory power created in section 2(2) of the European Communities Act 1972. My proposal has the twin advantages of being firmly anchored in authoritative legal materials and securing a further (and in my view desirable and appropriate) round of Parliamentary scrutiny when the decision is finally made.
(i) The Story So Far
First, there are signs that some on the continent have adopted the view that the referendum itself counts as the decision to leave. In their joint statement last week, the Presidents of the European Council, Commission and Parliament referred to the referendum result as a “decision” and invited the UK government to launch negotiations under Article 50 “as soon as possible”. And yesterday, the European Parliament adopted a text asserting that it is “the outcome of the referendum” which must be notified (immediately) to the European Council in order to launch the two-year withdrawal procedure provided for in Article 50.
This is plainly wrong. Under the United Kingdom constitution, the referendum does not count as a decision. It does not (unlike, for example, the referendum on the Alternative Vote in 2011) even oblige any other actor to make a decision. This point is often made by describing the referendum as “merely advisory” or “not binding”. Something more is needed, constitutionally speaking, before the decision to leave the European Union will truly have been made.
Two more plausible possibilities have dominated the domestic discussion. The conventional position has been defended by Mark Elliott, Carl Gardner and David Allen Green and is apparently presupposed in David Cameron’s approach to the issue. They argue that the decision to withdraw is within the government’s inherent prerogative power to conduct foreign affairs. On this understanding, whilst a decision is essentially politically inevitable it will be the government (in practice, the next Prime Minister) who will decide when and how the formal decision is made, without further scrutiny or any other kind of constraint.
Support is now emerging for a third view, according to which the prerogative does not extend to making the decision to exit the EU, and primary legislation would therefore be required to give effect to the outcome of the referendum. This view has been defended forcefully by Nick Barber, Tom Hickman and Jeff King and, for different reasons, by TT Arvind, Lindsay Stirton and Richard Kirkham. It has attracted some heavyweight support, including from Sir Stephen Sedley (in comments on this blog) and Lord Lester (in a letter to The Times). I think it is wrong: the executive does have the power to take the decision to leave the EU, but that power is not grounded in the prerogative:
(ii) The European Communities Act 1972
None of the three positions discussed above envisage the existence of a statutory answer to the question. But there is one. Section 2(2) of the European Communities Act 1972 provides (in the salient part) that:
any designated Minister or department may … make provision—
(a) for the purpose of … enabling any rights enjoyed or to be enjoyed by the United Kingdom under or by virtue of the Treaties to be exercised
Prior to Article 50, no Treaty right to leave the Union existed. The options which did exist either required unanimous agreement (treaty renegotiation) or were messy, uncertain and non-consensual (violation of Union obligations and possible eventual expulsion). Neither genuinely constituted withdrawal from the Union, which is why Article 50 was passed: Member states are now entitled to negotiate to withdraw on terms agreed to by only a qualified majority or (failing that) to withdraw unilaterally if no such agreement is reached within two years.
So now the United Kingdom enjoys, by virtue of the Treaty of Lisbon, two parallel novel rights: the right to pursue an orderly withdrawal even against the wishes of some other member states, and the right to withdraw unilaterally. But they can only be exercised once a decision to leave has been made (and notified). It follows that the decision to leave comes within the terms of section 2(2): it would be (in the 1972 statute’s unwieldy language) a decision for the purpose of enabling rights enjoyed by the United Kingdom to be exercised. In summary, section 2(2), a domestic statutory provision enacted by Parliament, provides a constitutional grounding for an executive (but not prerogative) power to make the decision to leave the EU under Article 50.
(iii) Two Consequences of the Argument
This has two important and inter-related consequences for the way the decision will be made. First, the existence of this statutory power to trigger withdrawal precludes the use of the prerogative power to pursue foreign affairs in this instance. The government has no choice; it must use the statutory power contained in the 1972 Act. Secondly the decision will be subject to the requirements of form and scrutiny to which that power is subject.
The relationship between apparently overlapping prerogative and statutory powers is governed by the test in Attorney-General Appellant v De Keyser’s Royal Hotel  A.C. 508. Lord Atkinson articulated that test (and its rationale) as follows (pp. 539-540, my emphasis):
[I]t would be useless and meaningless for the Legislature to impose restrictions and limitations upon, and to attach conditions to, the exercise by the Crown of the powers conferred by a statute, if the Crown were free at its pleasure to disregard these provisions, and by virtue of its prerogative do the very thing the statutes empowered it to do.
… such a statute … abridges the Royal Prerogative while it is in force to this extent: that the Crown can only do the particular thing under and in accordance with the statutory provisions and that its prerogative power to do that thing is in abeyance … after the statute has been passed, and while it is in force, the thing it empowers the Crown to do can thenceforth only be done by and under the statute, and subject to all the limitations, restrictions and conditions by it imposed, however unrestricted the Royal Prerogative may theretofore have been.
This means that if a statutory power is subject to more onerous conditions than the equivalent prerogative power, the executive cannot use that prerogative. The prerogative power to manage foreign affairs is thus superseded by the statutory power in section 2(2) to the extent that the 1972 Act imposes conditions on the exercise of that power.
Schedule 2 Para 2 provides that the Power to make an order under section 2 “shall be exercisable by statutory instrument”. Those statutory instruments “shall be subject to annulment in pursuance of a resolution of either House”, unless a draft has “been approved by resolution of each House of Parliament”. These conditions mean that the test in De Keyser’s is met and the decision cannot lawfully be made under the prerogative.
The conditions on the use of the section (2)2 power ensure a degree of formality and scrutiny when the government decides to trigger Article 50. It is hardly conceivable that the government would risk making a decision which would be vulnerable to subsequent annulment by a resolution of just one House. So it is almost certain that the statutory instrument making the decision to leave the EU would be presented for approval to both Houses. And it is fair to expect that in this instance, this is a responsibility that the Houses would take seriously, with the result that the decision to leave the EU would be the subject of a further round of effective debate in both Houses (although I have previously expressed some reservations about the rigour of that process). Successful passage following sufficiently rigorous deliberation would allow the decision to attain a level of legitimacy which would not be possible through direct use of the prerogative. On the other hand, if either House rejected the draft statutory instrument, then there would be an appropriate foundation for resort to primary legislation, moves toward the dissolution of Parliament and a general election, or both.
To summarise my argument:
(1) The European Communities Act 1972 gives ministers the power to make provision for the exercise of Treaty rights enjoyed by the United Kingdom.
(2) Article 50 creates such Treaty rights.
(3) Therefore the 1972 Act gives ministers the power to make provision for the exercise of the Article 50 rights.
(4) Under the rule in De Keyser’s Royal Hotel, this statutory power supersedes the equivalent prerogative power
(5) The exercise of this statutory power is subject to Parliamentary scrutiny.
Article 50(1) is very demanding on Member States; it presupposes that they have rigorous domestic procedures in place so that decisions to leave the Union can be legitimately made. This post has argued that we do have such procedures in place and that the constitution requires that they are followed.
Adam Tucker is Senior Lecturer at Liverpool Law School.
(Suggested citation: A. Tucker, ‘Triggering Brexit: A Decision for the Government, but under Parliamentary Scrutiny’, U.K. Const. L. Blog (29th Jun 2016) (available at https://ukconstitutionallaw.org/))