The Prime Minister has been sent a letter before claim — signalling that litigation may be in prospect — arguing that a second referendum is legally required before the United Kingdom can leave the European Union. The author of the letter, Dr Andrew Watt, bases his argument on the European Union Act 2011, which, in certain circumstances, does indeed require a referendum to be held prior to the ratification of treaties governing the UK’s relationship with the EU.

The effect of section 2 is that a treaty that “amends or replaces” the Treaty on European Union or the Treaty on the Functioning of the European Union cannot be ratified unless one or other of two conditions is fulfilled. The first condition is that the treaty in question is “exempt” from the requirements of the Act. The second condition is that a referendum on the treaty is held and ratification of the treaty supported by a majority of those voting in the referendum. According to Watt, section 2 of the Act means that no withdrawal treaty can be ratified unless approval is first obtained by way of a referendum.

Is Watt right — and does the possibility therefore arise of the courts stopping Brexit in its tracks, or at least pausing it while the will of the people is once again ascertained? If the Government thinks that this argument has any legs, it likely that it will seek to nullify it by providing in the “Great Repeal Bill” for the repeal of the relevant parts of the EU Act 2011. That would put any question concerning a second referendum beyond doubt. (A question might, however, remain about whether further legislation is required for the purpose of concluding — as distinct from triggering — the Article 50 withdrawal process.) Indeed, whether or not the Government is concerned about the sort of argument that Watt is making, relevant parts of the EU Act 2011 may in any event be repealed by the “Great Repeal Bill”.

But what if they are not? Does section 2 of the Act really require a second referendum? We know that the Prime Minister has said that “no deal … is better than a bad deal”, raising the prospect of Brexit taking place without any withdrawal agreement. In those circumstances, there could be no question of the referendum requirement in the EU Act 2011 applying, since there would simply be no withdrawal treaty upon which it could bite. If, however, there is a withdrawal agreement, Watt argues that section 2 — assuming it remains on the statute book at the relevant time — does require a referendum.

A withdrawal agreement, however, may well be a treaty that is exempt from the requirements of the 2011 Act, such that the referendum requirement does not apply. The central concern of the Act is the transfer of additional powers to the EU. As is clear from the Explanatory Notes that accompanied what was then the European Union Bill, the perceived mischief at which the Act was directed was the possibility of a Government, exercising its treaty-making prerogative, signing the UK up to new EU arrangements that would further tilt the balance of power in favour of the EU at the expense of Member States’ autonomy. In the light of that, very broadly speaking, treaties that do not have such effects are exempt from the referendum requirement in the 2011 Act. It is therefore likely that a treaty straightforwardly providing for the UK’s departure from the EU would be an exempt treaty: far from involving the augmentation of the EU’s powers in respect of the UK, it would extinguish them.

Watt, however, argues a withdrawal treaty would in fact be likely to result in the EU acquiring new competences over the UK, even if the net volume of its competences diminished. For instance, by rendering the UK a third state in respect of the EU, a consequential effect of a withdrawal treaty may (given that the UK seems destined to leave the Customs Union) be to enable the EU to impose tariffs on the UK. On this basis, it might be argued that a withdrawal agreement would not be an exempt treaty under the EU Act 2011, given that, according to section 4(1)(i), treaties are not exempt if they involve “the conferring on an EU institution or body of power to impose a requirement or obligation on the United Kingdom, or the removal of any limitation on any such power of an EU institution or body”.

However, that raises a broader question — not just about the scope of section 4(1)(i), but about the scope of the Act itself. The Act only applies in the first place to a treaty which “amends or replaces” the two principal EU Treaties upon which the UK’s membership of the EU is based: the Treaty on European Union and the Treaty on the Functioning of the European Union. In one sense, it could certainly be argued that a withdrawal treaty would “replace” the TEU and the TFEU. At present, those treaties regulate the UK’s relationship with the EU; but they will (assuming that the UK’s departure ends up being on agreed terms) subsequently give way to a withdrawal treaty and perhaps (at the same time or, more likely, subsequently) a trade agreement. In a factual sense, therefore, a withdrawal treaty would “replace” the TEU and the TFEU. But would it “replace” them in the legal sense in which that term is used by the EU Act 2011?

What the Act means by “replace” must be understood by reference to the underlying purpose of the Act. And it is arguable that its purpose is to regulate the exercise of the UK Government’s treaty-making powers vis-à-vis the EU in the context of the UK being a member of the bloc. Indeed, the Act exists in order to provide a direct democratic check upon the Government’s management of the terms of the UK’s membership of the EU, the idea being that there is a brake — in the form of the referendum requirement — upon any contemplated transfer of competence to the EU. On this view, the Act is concerned with treaties that shape the UK’s membership of the EU, not with treaties that are concerned with the termination of that membership or which provide for a post-membership relationship between the EU and the UK. In this way, it can be argued that a treaty providing for the UK’s departure from the EU would be outside the scope of the EU Act 2011, as would a treaty staking out a relationship between the UK and the EU that did not entail membership.

None of this is to deny that there is a strong political and democratic case for giving Parliament or (through a second referendum) the electorate a say when it comes to deciding whether any withdrawal agreement is satisfactory. But the argument that the law requires a second referendum is questionable — and, in any event, the relevant legislation may well have been excised from the statute book long before any withdrawal agreement is reached.

This post is based on a piece I wrote last year in response to a blogpost by Pavlos Eleftheriadis. The original post can be found here.