When he was Theresa May’s Foreign Secretary, Boris Johnson famously said, apropos of Brexit, that his ‘policy on cake’ was ‘pro having it and pro eating it’ — in other words, having the best of both worlds. Although the Prime Minister doubled down on that view yesterday, claiming that he had delivered the ‘cakeist’ fantasy that he had promised, the story of the last four and a half years has in fact been one in which the philosophy of ‘cakeism’ has entered into contact — slowly, ineluctably, and with utterly predictable results — with reality. That process has now reached its denouement in the form of the UK-EU Trade and Cooperation Agreement (the ‘TCA’) and associated Agreements, and the enactment of the European Union (Future Relationship) Act 2020, which gives domestic legal effect to the Agreements. So is the TCA, as the Prime Minister has told the BBC’s Political Editor, ‘a cakeist treaty’? Has Brexit proven to be a triumph that shows it really is possible to secure the best of both worlds?

Cakeism, of course, is a many-faceted philosophy that encompasses, among other things, international trade (leaving the EU customs union and single market while retaining all of the benefits of membership) and international relations (leaving arguably the world’s most powerful association of independent States while maintaining or even enhancing — remember ‘Global Britain’? — the UK’s international influence). My focus in this post, however, is on the legal and constitutional aspects of cakeism — and, in particular, on the question of whether its promises in this regard have been delivered, given that, now the end of the tortuous Brexit process has been reached, we are in a position to make an assessment. (Of course, it is not really the end, as even a cursory glance at the astonishingly complex institutional architecture established by the TCA demonstrates, but it is, at least, the end of this phase of the process.)

In legal and constitutional terms, two sets of related, but poorly differentiated, claims have been at the heart of the Brexit debate. The first is that membership of the European Union was incompatible with parliamentary sovereignty — a notion that Eurosceptics as they were, Brexiteers as they became, have fixated upon for decades — and that parliamentary sovereignty could be restored by leaving the EU. The second claim is that EU membership was inconsistent with a more diffuse notion of ‘national’ sovereignty and that, again, only departure from the EU could put things right on this front. Each of these claims is wrong in each of two respects. First, each claim is built upon the false premise that EU membership was incompatible with sovereignty; in fact, as I will argue, it was not. Second, each claim, judged on its own terms, is mistaken in assuming that sovereignty is ‘restored’ by leaving the EU; I will argue that, to the extent that EU membership, contrary to my first point, is considered to have involved restrictions on sovereignty, such restrictions are perpetuated by the terms on which the UK has exited the EU.

As far as parliamentary sovereignty is concerned, an enormous amount has been written about this over the last 40 or so years and it is unnecessary to rehearse the debate about whether, and if so how, it was possible to reconcile the primacy of EU law with the sovereignty of the UK Parliament. My own view, however, which I have set out at length elsewhere, is that there is no necessary tension between the two notions. The conceptual machinery necessary for facilitating the accommodation of the primacy and sovereignty doctrines was developed by the UK courts in a series of cases, most notably Thoburn and HS2, through the articulation of the idea of constitutional legislation. On this view, the European Communities Act 1972 was to be regarded as an Act of Parliament that enjoyed a ‘constitutional’ status that provided it with a degree of protection against (implied) repeal, thus enabling it to accord priority to EU law in respect of domestic legislation that did not explicitly attempt to revoke those priority arrangements. The idea that parliamentary sovereignty could co-exist with EU membership also received a ringing endorsement in the Supreme Court’s judgment in the Miller I case and was affirmed by Parliament itself in section 18 of the European Union Act 2011 (as well as, more recently, section 38 of the European Union (Withdrawal Agreement) Act 2020). Viewed thus, there was never any need to argue, as Sir William Wade famously did, that joining the EU amounted to a constitutional ‘revolution’ that sounded parliamentary sovereignty’s death-knell. It follows that if joining the EU did not vanquish the doctrine of the sovereignty of Parliament, leaving the EU does not restore the doctrine. On this view, sovereignty-loving Brexiteers have just solved a problem that never existed.

Moreover, even if, contrary to this argument, we were to be persuaded that EU membership did in fact involve a limitation upon parliamentary sovereignty, we would still be forced to conclude that, at least in conceptual terms, precisely the same sort of limitation will endure as a result of the Withdrawal Agreement. Looked at in this way, Eurosceptic adherents of parliamentary sovereignty have not merely addressed a non-existent problem: they have ended up doing so in a way that would fail to solve the problem even if it existed. So much is perfectly obvious from the Withdrawal Agreement and the domestic legislation that gives effect to it. Article 4(1) of that Agreement says that its provisions, along with those provisions of EU Law made applicable by it, ‘shall produce in respect of and in the United Kingdom the same legal effects as those which they produce within the Union and its Member States’, meaning that ‘legal or natural persons shall in particular be able to rely directly on the provisions contained or referred to in this Agreement which meet the conditions for direct effect under Union law’. In other words, the EU Law doctrine of direct effect — which gives automatic effect to directly applicable EU Law in Member States — applies to the Withdrawal Agreement. Meanwhile, Article 4(2) of the Agreement says that the UK, in order to comply with Article 4(1), must ensure that its ‘judicial and administrative authorities’ are able ‘to disapply inconsistent or incompatible domestic provisions’ by enacting ‘domestic primary legislation’.

The UK duly enacted precisely such legislation, providing in section 7A of the European Union (Withdrawal) Act 2018 (as inserted by section 5 of the European Union (Withdrawal Agreement) Act 2020) for the priority of relevant provisions of the Withdrawal Agreement over domestic law, including over Acts of Parliament. The means by which this is achieved is linguistically very similar indeed to the approach that was taken in section 2 of the European Communities Act 1972 in respect of the primacy and direct effect of EU Law. The upshot is that relevant parts of the Withdrawal Agreement enjoy direct effect and supremacy is a way that is conceptually identical to that in which EU Law was accorded direct effect and supremacy during the period of the UK’s membership of the EU. This, in turn, means that if Brexiteers wish to argue that EU membership entailed limitations upon the sovereignty of Parliament, they must, as a matter of logic, be forced to concede that Brexit on the terms that have been agreed — and by which the UK is bound in international law and for which the UK Parliament has legislated — give rise, so long as the Withdrawal Agreement remains in place and produces legal effects, to limitations of precisely the same conceptual form. It turns out, therefore, that on this front at least it is not possible to have one’s cake and eat it: it has not proven possible to leave the EU in a way that is both (a) acceptable to the UK Government and Parliament and which (b) removed such limitations upon parliamentary sovereignty as EU membership was (erroneously, in my view) considered to entail.

What, then, of the cakeists’ second claim, that EU membership limited sovereignty in a broader, more diffuse, ‘national’ sense, and that leaving the EU sheds such limitations and thus restores sovereignty to some sort of pristine, pre-existing form, unsullied by the bonds dthat have obtained this last near-half-century? This sort of argument has much preoccupied Brexiteers such as those who make up the Conservative Party’s ‘European Research Group’, and whose ardour for the notion of ‘sovereignty’ verges on fetishism. When the draft TCA was published, the ERG convened its so-called Star Chamber to review the Agreement. In its paper on this matter, the ERG framed the ‘essential question’ as whether the TCA was ‘sovereignty compliant as a matter of law’. Happily for the Prime Minister and for its members, the Group’s lawyers concluded that ‘[t]he Agreement reaffirms the sovereignty of the United Kingdom’. But what on earth does that mean?

In unpacking this question, it is important to bear in mind the subtext that, for at least some Brexiteers, membership of the EU was always flatly irreconcilable with the sovereignty of the UK as a State on account of the fact that the UK was obliged, as an EU Member State, to play by the rules of EU — notwithstanding that the UK was bound only because it had chosen, and only for as long as it wished, to be. Particular exception was taken (and here Brexiteers begin to elide their concerns about State and parliamentary sovereignty) to notions such as the direct effect of EU Law, its primacy over domestic law, its curation by the Court of Justice of the European Union (which has always been a particular bogeyman for Eurosceptics), and the possibility of a Member State being bound by EU Law to which it had not itself agreed, thanks to the possibility of EU legislation being adopted against individual States’ wishes under the arrangements for qualified majority voting. It is no surprise, therefore, that in concluding that the TCA ‘reaffirms the sovereignty of the UK’, the ERG expresses palpable relief at the fact that the Agreement does not ‘provide a role for the [Court of Justice]’ and that ‘the EU approach of provisions having “direct effect” in UK law is excluded’. (But of course the Withdrawal Agreement, as distinct from the TCA, does make provision for precisely such matters.)

What is particularly striking is the level of cognitive dissonance that is on display in the ERG’s ‘legal opinion’ when it comes to the ‘rebalancing’ provisions of the TCA: that is, the provisions that allow the imposition of tariffs in certain circumstances in the event of regulatory divergence that breaches the level playing field requirements that are axiomatic to the Agreement. The ERG concludes that there is no need to be concerned about these arrangements amounting to a ‘constraint’ on UK sovereignty because of the legal limitations imposed by the Agreement on each side’s capacity to apply tariffs and the opportunity to challenge the imposition of tariffs in arbitration proceedings. This appears to reduce to the argument that sovereignty is not unduly threatened because the ‘price’ of exercising sovereignty (tariffs) is subject to regulation by a quasi-judicial process (arbitration). Is this not, however, conceptually the same as, or at least very similar to, the position that applied to the UK while it was a Member State? EU Member States are bound by the EU Treaties, and thus EU Law. If they exercise their national ‘sovereignty’ in a way that is inconsistent with their Treaty obligations, a price must be paid — a price that is liable, in the first instance, to take the form of financial penalties imposed by judicial process. Similarly, the UK, post-Brexit, will have the option of exercising its sovereignty by way of departure from the level playing field provisions of the TCA but, should it choose to do so, will have to pay the relevant price by accepting the imposition of tariffs.

Indeed, in one sense, it can be argued that the UK — in ‘sovereigntist’ terms — is now, post-Brexit, in a weaker position. While it was a Member State, it had a seat at the table and was able to influence the content of the obligations it was required to abide by. In contrast, following Brexit, the UK, if it wishes to avoid the imposition of tariffs, becomes a rule-taker rather than a rule-maker, in that it has no option but to align itself with a regulatory model designed exclusively by EU Member States — which, needless to say, the UK no longer is. Once again, then, cakeism rings hollow. The UK has not, through the TCA, landed upon an ingenious means by which to benefit from tariff-free access to the Single Market while escaping the EU’s regulatory orbit. Rather, the UK has agreed to become a rule-taker in exchange for tariff-free access, and to pay, by means of accepting the imposition of tariffs, for the privilege of exercising its sovereignty should it wish to effect regulatory divergence.

There is, however, a deeper level at which the ‘having one’s cake and eating it’ philosophy breaks down in relation to sovereignty in this broader, ‘national’ sense. This concerns the underlying premise that sovereignty is the sort of concept that can meaningfully be ‘maintained’, ‘preserved’ or ‘recovered’ — language that forms a critical part of the Brexiteer argot. This view presupposes that sovereignty in this sense is a binary concept: something that a State either has or has not; something to be given away or to be recovered. This, however, is to fundamentally misconceive what sovereignty is. Far from being a binary concept that either is or it not possessed, sovereignty is a resource that States are capable of deploying in an infinite variety of ways. Accepting ‘limitations’ upon sovereignty by entering into legally binding international arrangements is, in truth, a means of exercising sovereignty, whereby the legal resources of the State are harnessed in the service of objectives that are judged, in political, economic, diplomatic or other terms, to be worthwhile — and, critically, to warrant the reduced freedom of action thereby entailed.

EU membership involved precisely such a deployment of the UK’s sovereign resource, just as the TCA involves ‘using’ sovereignty to secure certain outcomes in return for an acceptance of certain consequences. For present purposes, which, if either, of those ‘sovereignty transactions’ is the better one is neither here nor there. The critical point is that they are both such transactions — to pretend otherwise, by claiming that EU membership denied UK sovereignty while the TCA re-establishes it, is nonsensical. Sovereignty is not a relic to be hoarded; it is a resource that necessarily has to be used in an interconnected world, and which the UK, having left the EU, will (have to) continue to use, just as it has done by entering into the TCA. The sooner that is recognised on all sides, the sooner it will be possible to move beyond the too-often intellectually vacuous debate that has characterised discourse of the UK’s relationship with the EU over the last half century, and which has too frequently shaped the conversation about Brexit during the last four and a half years. Discussion about how the UK trades and interacts with the EU is far from over, not least because the TCA itself leaves so much unfinished business. It is to be hoped (although it is most likely a vain hope) that now those who agitated for it think that ‘Brexit is done’, a more grown-up conversation might in the future be possible. If that hope is to be realised, engaging with the real issues, shorn of appeal to the so-often-misunderstood language of ‘sovereignty’, will be imperative.

I am grateful to Jack Williams of Monckton Chambers for his comments on an earlier draft of this post.