The litigation concerning the triggering of Art 50 TEU is under way, with hearings this past week and early next. It is the constitutional case of the century. The Government’s skeleton argument has been published. This reveals that one of the pillars of its defence is that the decision to withdraw from the EU has already been taken. Consequently, all that is in issue is the authority to notify the EU of that decision, and to start the two-year period provided for in Art 50. That, the Government’s case goes, is a decision of high policy which is rightly in the Government’s hands, and not in those of parliament.

In an excellent blog post, Mark Elliott and Alison Young dissect and critique this framing of the litigation. They point out that it is difficult to identify who took the momentous Brexit decision, given that the referendum was advisory and there is no formal government decision either – only political statements. Their critique is informed by UK constitutional authority.

In this blog I also want to focus on this question, but more from an external and EU law perspective. The theses I want to present are twofold. First, and at the expense of coming across as completely divorced from reality, I argue that there is as yet no Brexit decision. Second, if the principle of UK parliamentary sovereignty is to continue to have real meaning, the decision has to be taken by Parliament, not the Government.

Ever since the debate about the respective roles of Parliament and Government in the Brexit process gathered steam, there has been an excessive focus on the notification question: is it for the Government to “trigger” Art 50 by notifying the EU, or is it for Parliament? This kind of framing of the debate overlooks the wording of Art 50 TEU. The first paragraph of that provision proclaims that “any Member State may decide to withdraw from the Union in accordance with its own constitutional requirements”. The second paragraph states that “a Member State which decides to withdraw shall notify the European Council of its intention”. So first, there must be a constitutionally orthodox decision to withdraw. The notification is secondary.

The first paragraph of Art 50 distinguishes that provision from standard treaty clauses governing termination. Those clauses usually conflate the withdrawal decision and its notification. They reflect a traditional international law and international relations paradigm, according to which foreign affairs are mostly a matter for the executive. The clauses themselves do not mention the executive, but they treat states as unitary actors, and the practice is simply that the state expresses itself internationally through executive action. It is the government which acts on the international plane. How such executive action comes about as a matter of domestic law is irrelevant, except in blatant cases (see e.g. Art 46 on provisions of internal law regarding competence to conclude treaties). By contrast, Art 50 expressly requires that there is first an internal decision to withdraw, adopted in accordance with the Member State’s own constitutional requirements. Once that decision has been taken, the Member State must notify, and I have no issues whatsoever with the position that this is properly governmental action. Indeed, it is the European Council which needs to be notified, and that EU organ is itself composed of heads of state and government. Nor would I argue that it is for any actor other than the Member State concerned to determine what its own constitutional requirements are, for taking the withdrawal decision. The other Member States and the EU institutions do not, on the face of things, have the power to review whether the withdrawal decision is constitutionally orthodox.

And yet the reference to such a constitutionally orthodox decision is critical. The EU is not a classical international organisation. It establishes an ever closer union among the peoples of Europe (Art 1 TEU). It is founded on representative democracy (Art 10 TEU), with both direct representation (in the European Parliament) and indirect representation (democratically accountable governments acting in the European Council and in the Council). EU law directly confers rights on individuals (Van Gend en Loos). These rights are extensive and meaningful, ranging from free movement, over trade, to fundamental rights in the EU Charter, including social rights, to a panoply of rights in EU legislation (consumer rights; environmental rights; rights to agricultural subsidies; company law rights; transport rights; rights to enforce foreign judgments; rights to asylum; etc etc). As far back as 1974 Lord Denning likened the then EEC Treaty to an incoming tide, flowing into the estuaries and up the rivers, and said that it could not be held back because Parliament had decreed that it was part of UK law. It is undeniable that the tide has waxed tremendously, but the point remains the same. EU law is automatically part and parcel of UK law for as long as the UK is an EU Member State. Or for as long as Parliament maintains the effect of EU law, through the European Communities Act 1972.

It cannot therefore come as a surprise that Art 50 requires that a decision to withdraw be taken in accordance with a Member State’s constitutional requirements. Indeed, in a large majority of other EU Member States the constitution makes provision for EU membership, and withdrawal would require constitutional amendment.

Much of this EU law orthodoxy may not be to the liking of Brexiteers and Leave voters. But if the UK chooses to withdraw in comformity with its international obligations, rather than through some type of revolutionary act, Art 50 must be taken seriously. And these international obligations are not trivial, precisely because they have created all these rights, effectively for the whole of the populations of both the UK and of the other Member States.

So when the matter is looked at from an EU law perspective, there is a great legal question looming over Brexit: has the decision to withdraw been taken, and if so when and by whom? I fully realise that even asking this question invites ridicule. Politically, the Brexit decision is a fact. But politics and law are distinct, and for good reason, as a core function of the law is to constrain politics in order to establish and safeguard liberal democracy. And from a legal perspective, the difficulty of locating the Brexit decision needs little elaboration. Parliament organised the referendum without spelling out its consequences, and it is generally accepted that the vote was merely advisory in the legal sense. There is no formal Government decision to withdraw, nor has Parliament taken such a decision. Just read the Government’s skeleton argument in the current litigation and Elliott and Young’s blog to see for yourself what intellectual contortions are required to argue that there is indeed a Brexit “decision”.

Why is this the case? For the following reasons I would surmise. The present Government does not want to recognise that the Brexit decision is for Parliament because it fears that the parliamentary debate may turn out to be uncontrollable, and lead to constraints on its margin of discretion in negotiations. Besides, institutions usually claim that they have the power to do things themselves. But nor is the government willing to adopt a formal Brexit decision, separate from its notification, because that would expose that decision’s lack of constitutional orthodoxy. I do not claim great expertise in UK constitutional law. But looked at from a distance, what is really left of the sovereignty of the UK parliament if a decision as seismic as that of withdrawing from the EU, a decision which entails the effective revocation of the European Communities Act 1972, this enormous estuary through which all these EU law rights flow into the UK, can be taken by the Government and does not require an “Act” of Parliament? Of course, the people have voted. But it is equally obvious that Parliament did not fully contract out the withdrawal decision.

I wish to state emphatically that I do not think that the UK Parliament should kick Brexit into reverse. That would be an affront to the vote, and thus to democracy. But there is a clear need for Parliament to get involved because the British people (and indeed those from other Member States affected by Brexit) deserve an open debate among democratically elected representatives about what Brexit means, and how best to organise the future relations between the UK and the EU. And I think it would put the UK in a much better negotiating position if its proposals emanated from such democratic debate, rather than from mere cabinet meetings and Conservative party cenacles.

Piet Eeckhout is Professor of European Law and Vice-Dean of the Faculty of Laws, UCL.

(Suggested citation: P. Eeckhout, ‘The UK Decision to Withdraw from the EU: Parliament or Government?’, (15th Oct 2016) (available at https://ukconstitutionallaw.org/))