1. Closure or New Opening?
Referendums are supposed to provide decisive interventions in the affairs of state. They are designed to produce clear ‘yes or no’ answers to large political questions. And as these answers also come with a rare level of popular endorsement, this should facilitate their effective and timely implementation.
That, at least, is the theory. And the tone and rhetoric of the referendum campaign would seem to back up the theory. The one thing that both sides appear to be agreed on, and which accounts for the increasingly febrile atmosphere of claim and counter-claim, is that the choice before us is a stark one. In terms of constitutional futures it is a binary vision of ‘in’ or ‘out’ that increasingly dominates, a crude black and white landscape with all shades of grey banished.
Yet we should not be fooled by the rhetoric, for key features of the wider legal and political context of the ‘Brexit’ referendum suggest a much more nuanced picture. Of course the verdict – a vote for staying in or for leaving the European Union – will have a major influence on what follows. Yet the post-referendum process, and the outcomes it will help shape, remain shrouded in uncertainty and dependent on a wide range of consequential choice-options on the part of various parties. Whatever the result, we can look forward to a lengthy and unpredictable journey to an incompletely mapped destination.
The procedure for exiting the European Union (EU) is sketchy, untested, and offers little guidance as to possible conclusions. And if, instead, as the opinion polls narrowly favour, Britain votes to remain, then the new deal negotiated with the EU in February of this year as a condition of the British Government’s support for a ‘Yes’ vote must overcome various obstacles before it achieves full legal and political effect. Furthermore, whatever the verdict, and however the post-vote process is resolved, the long-term substantive implications of the referendum for Britain’s relationship with Europe remain uncertain. To put matters bluntly, at least according to most shades of political opinion, European ‘membership’ for a country of Britain’s size, influence and location is less a matter of ‘yes or no’ than one of ‘more or less’. There are various models of engagement with the EU available to the UK in the future. And whichever model – or combination of models, in fact emerges depends not only on the vote, or even on the power politics and evolved preferences of the British post-vote negotiations. In addition, the long-term outcome will be influenced by developments in the broader (self)-understanding of the EU as a post-national legal and political order, and, in particular, by how the relationship amongst the Member States and between these Member States and various categories of neighbours and associates is viewed as part of that broader understanding.
In a nutshell, the referendum will not mark the closure of the story of the legal and political relationship of the UK to the EU, but a new opening. Let us now explore both aspects of this open horizon – first, the post-vote process and, secondly, the range of substantive models of engagement with the EU available to the UK in the longer term.
2. The post-referendum process
a. In the event of a ‘No’ vote
Article 50 of the Treaty on European Union outlines the procedure for a Member State wishing to withdraw from the European Union as follows:
1. Any Member State may decide to withdraw from the Union in accordance with its own constitutional requirements.
2. A Member State which decides to withdraw shall notify the European Council of its intention. In the light of the guidelines provided by the European Council, the Union shall negotiate and conclude an agreement with that State, setting out the arrangements for its withdrawal, taking account of the framework for its future relationship with the Union. That agreement shall be negotiated in accordance with Article 218(3) of the Treaty on the Functioning of the European Union. It shall be concluded on behalf of the Union by the Council, acting by a qualified majority, after obtaining the consent of the European Parliament.
3. The Treaties shall cease to apply to the State in question from the date of entry into force of the withdrawal agreement or, failing that, two years after the notification referred to in paragraph 2, unless the European Council, in agreement with the Member State concerned, unanimously decides to extend this period.
4. For the purposes of paragraphs 2 and 3, the member of the European Council or of the Council representing the withdrawing Member State shall not participate in the discussions of the European Council or Council or in decisions concerning it.
A qualified majority shall be defined in accordance with Article 238(3)(b) of the Treaty on the Functioning of the European Union.
5. If a State which has withdrawn from the Union asks to rejoin, its request shall be subject to the procedure referred to in Article 49.
History offers no help in understanding this text. There is no precedent for a Member State making a formal commitment (as opposed to an informal threat, as, for example, in the case of Greece during the stand-off between Syriza and the EU centre last year over the management of Greece’s indebted economy) to leave the European Union, either before or since the introduction of the Article 50 dedicated exit mechanism under the Treaty of Lisbon in 2009. And so the bare formula procedure remains uninformed by prior experience and untested in practice. We can, however, highlight a few of its key implications and identify some of the main questions it raises.
The two-year period stipulated under Art. 50(3) imposes no hard and fast deadline. If after two years have elapsed a withdrawal agreement still has not been concluded, the UK as the exiting Member State will nevertheless remain in the EU club, and so subject to the Treaties pending the conclusion of such an agreement, unless the UK or at least one of the remaining Member States (as represented in the European Council) prefers an un-negotiated withdrawal to the continuation of negotiations. Is it likely that either the UK or any of the Member States will refuse or discontinue negotiations? On the one hand, given the longstanding interdependence of the UK and the EU, not least as close trading partners and with a considerable interflow of populations under a common citizenship regime, it is difficult to envisage the circumstances under which it would be in either of their interests to allow an un-negotiated withdrawal to happen. On the other hand, as an agreement to extend the timetable has to be unanimous amongst the remaining Member States, in a climate of post-Brexit coolness (if not hostility) towards the UK it is less difficult to envisage at least one such Member State losing patience when faced with the prospect of protracted negotiations.
However lengthy the negotiations turn out to be, Art. 50 provides little indication of the possible content of the withdrawal package. One thing that is certain, however, is that withdrawal means withdrawal. Art. 50(5) makes it clear that, despite some suggestions to the contrary from Brexit supporters who have from time to time mooted the possibility of a second referendum to consider a new deal that they believe might be forthcoming after an initial ‘no’ vote, the withdrawal process cannot be a pretext for the negotiation of new membership terms. Instead, a state wishing to alter its terms of membership would have to go through the same full and exacting accession process under Article 49 TEU as any new Member State, and would do so in a climate of negotiation hardly improved by its recent resolution to leave. Quite apart from the general erosion of mutual trust post-divorce, the EU is likely to be strategically minded to adopt a tough negotiating stance so as to discourage others from following the UK example.
Significantly, however, Article 50 does seem to countenance and, indeed, to facilitate some degree of continuity of relations. There is a positive requirement of negotiation on the part of the Council, which will open the negotiations after having received recommendations from the European Commission. There is no requirement of unanimity on the European side as regards the conclusion of the withdrawal agreement. All that is required is the consent of a so-called ‘super qualified majority’ of the Council (at least 72 per cent of the continuing members, representing at least 65 per cent of their population), and also the European Parliament. This means that, even though, as we have seen, a reluctant or hostile continuing Member State could veto the extension of negotiation beyond two years in the absence of an agreement, it will not be able to veto an agreement that has already been accepted by the other continuing parties and the exiting party within the two year limit. What is more, the form of the agreement envisaged under Art. 50 is that of an international agreement, which covers a wide range of relationships, including - as we shall see - quite close forms of association.
There is likely, however, to be a significant trade-off between the depth and intensity of continued association on the one side, and the speed and certainty of what is negotiated in the withdrawal agreement itself on the other. To the extent that a withdrawal agreement might be devised as a platform for the continuation of a close form of association, this would probably require further and more extensive agreements, and so an additional and indeterminate extension of the timetable for the resolution of the UK’s exit. A more extensive agreement regulating, say, the UK’s continuing involvement in the single market, might by dint of the interests it affects, more appropriately be of a ‘mixed’ variety; that is to say, one that requires to be concluded and ratified by all the Member States as well as the EU. And the implementation of the withdrawal agreement, and any further and more extensive agreements, would likely also require amendments to EU law; in turn, this would involve further Treaty change requiring the unanimous approval of the remaining Member States under the general amendment mechanism of Art. 48 TEU, as well as other reforms using existing legislative procedures and competences involving European Council, European Commission and the European Parliament. And, of course, just as the UK would not be party to the formulation of the EU position in the negotiation of the basic withdrawal agreement (as Art.50(4) makes clear), as the exiting Member State it would have no say in the adoption of any consequential laws or policy positions from the EU side.
No-one can predict how long this fuller process of withdrawal would take, as much would depend on the preferred exit model of the UK government (see section 3 below) and the speed at which relations with Europe might recover. Yet perhaps the estimate of one retired senior civil servant that it might take up to ten years should not be dismissed out of hand.
b. In the event of a ‘yes’ vote
Three years of renegotiation of the terms of British membership intended to persuade the British public to vote ‘yes’ culminated in a meeting of the European Council on 18-19 February 2016 at which a new settlement was drafted. The new settlement, which includes six legal texts and promises many more, and which will come into effect only in the event of a ‘Yes’ vote in the June referendum, covers:
removal of the foundational Treaty commitment to ‘ever closer Union’ for the UK;
augmentation of the powers of national parliaments to object to a draft EU legislative proposals on the grounds of subsidiarity, through the introduction of a ‘red card’ procedure ;
In the area of economic governance (including Banking Union and emergency mechanisms for preserving the financial stability of the Euro), the introduction of safeguards against measures of economic governance within the Eurozone that may be prejudicial to the interests of non-Eurozone states, including the UK, while at the same time ensuring that non-Eurozone states do not provide unnecessary obstacles to further integration within the Eurozone;
With regard to social benefits and free movement; blocking or reducing in-work benefits for migrants where there is an inflow of workers from other Member States of such a magnitude as to put pressure on the social security system or other public services or so as to affect the employment market; restricting the level of child benefit which can be sent abroad to other EU states; and increasing the powers of states to limit entry on grounds associated with public security and the abuse of free movement and residence rights through devices such as forged documents and marriages of convenience.
The enhancement of competitiveness within the single market, in particular through lowering administrative burdens and compliance costs on economic operators - especially small and medium size enterprises.
With the exception of heading (v), which is couched in extremely general terms and in any case in line with the current orientation of European institutions, these initiatives are complex and controversial. This is not the place to examine their content in any depth. What is worth stressing, however, consistent with our theme of protracted uncertainty, are the difficulties associated with translating the relevant commitments into effective legal measures.
The stated objective of the British Prime Minister in the months and years before the February European Council was to obtain an agreement that was ‘legally binding and irreversible’. In one limited sense, that objective has been achieved, and, indeed, the European Council affirmed this to be the case, but this conclusion should not be read as implying an unobstructed path to implementation. Crucially, the key Decision taken by the Heads of State or Government on the occasion of the February European Council, once registered as an international treaty, will indeed be binding (and irreversible, except with the consent of the UK as one of the parties to the treaty), but only as a matter of international law, not EU law. For the various provisions of the Decision to become part of EU law does not automatically follow from their status as international law, but will require further implementing measures.
Both the exemption of the UK from the commitment to ‘ever closer Union’ and the broad changes contemplated in the relationship between the Eurozone and non-Eurozone states will require Treaty amendments, involving the consent all EU states and ratification by their national parliaments. Some of the more detailed measures will have a much less onerous passage. Certain alterations of voting rules as regards certain Eurozone regulations can be brought about by the Council acting alone, whose support is already committed by the terms of the February agreement, as can the introduction of a new subsidiarity-centred procedure for discontinuing the Council’s consideration of a new legislative measure upon its receipt of a ‘red card’ from national parliaments. Other parts of the deal, however, in particular the measures on child benefit, on the restricted entry of non-EU family members of EU citizens, and on the introduction of an emergency brake blocking the in-work benefits of migrant workers for a maximum of four years, require EU legislation. As such, they must command the support not only of the Council, but also of the Commission and the European Parliament. The Commission’s support is guaranteed in principle through a series of Declarations attached to the February Agreement by which it undertakes to propose the necessary legislation if and when a ‘Remain’ vote is assured. But there are no guarantees – soft or hard – as to how the European Parliament will respond to new proposals, or, further down the line, on how or whether the emergency brake on in-work benefits – introduced with the UK case specifically in mind but couched in general terms and requiring a closely contextual assessment and decision by the Commission and the Council, will be effectively applied in the instant case. And finally, nothing that has been agreed offers any guarantees as to how the Court of Justice, as the ultimate guarantor that the EU’s actions are in accordance with EU law, will interpret the various aspects of this multi-faceted and multi--staged agreement.
The absence of a watertight, closely timetabled legal settlement becomes all the more significant when one consider the political difficulties associated with its implementation. The cases of Ireland and Denmark, both of whom negotiated exceptional and supplementary measures to overcome stalled national ratification procedures under earlier Treaties, are often cited by supporters of the deal as reassuring precedents. But the political context is much different, as is the scope for legal challenge. In these earlier cases, Ireland and Denmark were asking for partial exceptions to new provisions they had never agreed, not for a unilateral rejection of a menu of existing Treaty obligation previously agreed with and implemented by them and everyone else. What is more, some of what has been agreed in the new deal arguably challenges core aspects of the 60 year EU settlement. The UK exemption for ‘ever closer Union’ could be construed as reneging on a founding common commitment, while the restrictions on movement and welfare benefits challenge cardinal principles of non-discrimination on grounds of nationality and free movement of workers.
Of course, the fact that these terms become operative only in the event of a ‘Yes’ vote means that any hostility and lack of co-operation on the EU side should be much less than under the exit scenario considered above. But even if asking for special treatment is diplomatically preferable to leaving, we should not underestimate the lingering resentments that might frustrate the completion of what will in any event be a drawn-out process of accommodation.
3. Models of post-Referendum engagement with EU
a. Differentiated integration
The idea that some states should be subject to different rules than others within the framework of the EU is hardly novel. In the early days of European integration there was much resistance to the concept of differentiated integration as it was seen to detract from the founding ideal of a uniform set of commitments to the pooling of national sovereignty. Since the 1990s, however, in response to the development of a deeper and wider range of EU competences beyond the single market core, as well as to successive waves of enlargement to the present 28 members, differentiation has emerged in the majority of areas of EU policy. The most prominent cases are Economic and Monetary Union, with membership of the Eurozone gradually increasing from 11 to 19, and the Schengen Agreement on open borders, signed by 5 out of the then 10 members 30 years ago and today comprising 26 members, 22 of whom are EU members. Yet this is only the tip of a much larger iceberg, with as many as 50 different cases of differentiation provided for under the EU treaties.
What is more, there are a number of different general models of differentiated integration vying for ascendancy within today’s complex and ever-shifting supranational institutional architecture. The most conservative such model, albeit increasingly outstripped by practice, is known as ‘multi-speed Europe’, where a core group of countries moves forward at a faster pace than the others, but with the expectation that the others will catch up in due course. A Europe of ‘variable geometry’ or ‘concentric circles’ offers a more radical – but in the view of many increasingly more realistic - vision in which the core or inner circle opts for deeper level of integration than the outer circle(s) of membership on a permanent or indefinite basis. A third model, commonly referred to as Europe ‘a la carte’, is most flexible in its accommodation of difference, and for that reason an enduringly difficult fit with the overall aims of the EU. It would allow states to opt for more or less integration depending on the issue area, provided they adhere to a general set of common EU objectives.
To a greater or lesser degree across these various models, differentiation promises a degree of flexibility that offers both micro-political and macro-political advantages. At the micro-level, it tracks particular national preferences for more or less integration in various policy areas. At the macro-political level, it allows from some kind of accommodation between ‘supranationalists’, who seek deeper economic and political integration and do not want that aim to be diluted by successive waves of Enlargement, and ‘intergovernmentalists’, who want to guard against a political imperative which requires all to integrate at the rate of the most Europhile states.
The UK has always benefited from differentiation from the ‘intergovernmentalist’ side of this divide. It is a member neither of Schengen nor of the Eurozone, possesses other significant opt-outs in immigration and criminal justice co-operation under the Area of Freedom, Security and Justice, and has from time to time enjoyed other exemptions - for example, from the Social Chapter between 1992-7, and, today, from the full effects of the Charter of Fundamental Rights of the European Union. What is more, the decision of the EU Heads of States or Government, made as recently as 2014, to endorse the idea of ‘different paths of integration for different countries’ as being perfectly compatible with the maintenance of a common commitment to an ‘ever closer Union’ was intended, inter alia, to assure the UK that it did not need to take a unilateralist stance to accommodate its particular relationship with the EU. 
As we now know, that particular gambit failed. Even many of the ‘Yes’ supporters in the referendum do not consider the existing multilateral framework of differentiated integration sufficient to meet Britain’s needs and concerns; hence Cameron’s insistence on a future exemption from ‘ever closer Union’ Yet the picture remains a complex one, and the distinctions between the many positions on the table are not clear-cut. It is certainly the case that at an earlier stage of negotiations before the in/out referendum was proposed, the Conservative Government did seek to advance its arguments for Treaty reform in multilateral terms, favouring a two-tier, ‘variable geometry’ conception of the EU with a Eurozone core and the UK included in a less integrationist outer circle. And, importantly, even now there remains a significant degree of architectural continuity between, on the one side, the various multilateral models of differentiated integration that are available and, on the other side, not only the unilateral conditionality pursued by the UK government in support of continued membership but also some of the options available and under consideration on the Brexit side of the argument.
As we have seen, Cameron’s new deal for remaining, although unilateral in initiative, is actually multilateral in content with the exception of the exemption from ‘ever closer Union’. And, from the ‘Leave’ perspective, some of the options for continued external association, we shall see, assume the retention of quite a high level of common regulation with the remaining members, as is already the case with a number of other non-member neighbours of the EU. Tellingly, indeed, in the wider literature on differentiated integration, some writers talk about the difference between ‘internal differentiation’, which embraces members only, and ‘external differentiation’, which extends to non-members, as being one of degree rather than kind (the key Schengen agreement which excludes some EU members and includes some non-members being a prominent case in point). It follows that some of the general models of differentiation considered above may be extended to cover the situation of non-members as well as members.
In sum, where the legal architecture is in any case complex and non-uniform, the distinction between members and non-members, and between the different combinations of common and distinctive regulation available on either side of the membership divide, becomes less precise, and also, we shall see, more fluid and more subject to fluctuation, than is often appreciated, or least conceded, from the binary yes/no perspectives of the referendum debate. With this thought in mind, let us now consider the various models of post-referendum engagement with the European Union that are available.
b. Models of Engagement
If Britain votes to leave, we can imagine three broad categories of continued engagement or re-engagement with the EU.
i. The Norwegian Approach – joining the European Economic Area
The European Economic Area (EEA) was founded in 1994 and now comprises Norway, Iceland and Liechtenstein plus the present 28 Member States of the EU. All members of the EEA are part of the single market. This means that the free movement of goods, services, people and capital, which supplies the first base of economic integration in the EU, also extends to the EEA area. This also means that EU rules concerning the common regulation of the market in areas such as employment, consumer protection, environmental standards and competition policy must be adhered to by EEA members. Free trade within the EEA, however, is not matched to membership of the EU’s customs union, and so EEA members can set their own external tariffs and develop their own trade policy with countries outside the EU. There is no obligation, moreover, to participate in Monetary Union, Common Foreign and Security Policy, or Justice and Home Affairs, and EEA members cannot participate in the Common Agricultural Policy.
If this suggests the retention of many of the benefits of membership of the world’s largest single market without the requirement of deeper integration, there are also clear disadvantages. EEA members must contribute to the costs of the EU programmes in which they participate and also to the EU’s regional development funds. This can be very significant. In 2011, for example, Norway’s contribution to the EU budget was £106 per capita, only 17% lower than the UK’s net contribution of £128 per capita. Exclusion from the EU’s customs union can also lead to the restriction of the entry of UK goods into the EU unless they pass strict ‘rules of origin’ tests, and can also make the EEA country susceptible to EU anti-dumping measures (intended to restrict market-undercutting import levels and prices in particular goods). In addition, while the UK would have to implement all regulations pertaining to the single market, including the highly sensitive area of the free movement of persons, they would no longer have voice and vote in the making of such regulations., Instead, they would be restricted to a consultative role, and would be required to harmonise their views with the other EEA members in developing a common position towards the EU.
In terms of the models of differentiated integration discussed above, this version of external differentiation correspond most clearly to a concentric circles or variable geometry model, with the UK as part of a third circle of EEA members and various other (central and eastern European) states under the umbrella of the EU’s neighbourhood policy, situated beyond not only core EMU and Schengen states but also others with significant opt-outs such as Denmark and Ireland yet who nevertheless remain Member States. The savings of non-membership in terms of financial contribution and exemption from areas in which the UK did not want to participate would be limited, while the costs in terms of lost influence over EU law and policy would be significant. What is more, the Association Agreement necessary for membership of the EEA, as a mixed agreement, would require the consent not only of the EU but each and every other member of the EU (and the EEA) in accordance with their own national constitutional requirements. As the recent example of the failed Dutch Referendum on the EU-Ukraine Association Agreement demonstrates, this remains a hazardous route - not least as it would follow on so shortly after the conclusion of divorce proceedings.
ii. The Swiss Approach – a set of bilateral treaties
A second alternative is the Swiss model, which involves membership neither of the EU nor of the EEA but the negotiation of a series of bilateral treaties governing relations with the EU in specific areas of common interest. At the core of this lies the preservation of a free trading relationship with the EU in which UK non-agricultural goods are guaranteed tariff-free access to the EU and vice-versa. In the UK’s case this would probably be assured through re-joining the European Free Trade Association (EFTA) – which was founded in 1960 as an alternative to the EU – with the UK as a prime mover - and which presently comprising the three non-EU EEA states as well as Switzerland. However, technical barriers to trade in goods, trade in services and free movement of persons are not covered by EFTA rules and would have to be the subject of separate bilateral agreements, as they are to varying degrees in the Swiss case.
This approach is closer to the a la carte model of differentiated integration discussed above. In theory, it would allow more freedom for the UK to negotiate a bespoke model of engagement with the EU. But many of the objections that may be made to the EEA model apply here too. The UK would lose voice but retain significant financial obligations to the EU. Moreover, the flexibility of a purely bilateral and piecemeal approach generates high and repetitive transaction costs, and with an EU partner which would be under no obligation to offer everything on the list, and which might, indeed, insist upon a ‘set menu’ of combined options. (e.g., free movement of persons as a condition of the continuation of a single market in services)
iii. The WTO fall-back
Recognizing the weight of some of the arguments against these models, Leave campaigners have increasingly sought to emphasize a more free-standing approach in an international order generally committed to the removal of trade barriers. The UK remains one of 161 member of the World Trade Organisation committed to a ‘most favoured nation’ standards of common transnational market access. Crucially, however, the level playing field offered by the WTO contains a number of exceptions, including regional organisations such as the EU. And so while the UK could not be discriminated against by the EU in terms of tariff barriers compared to the EU’s ‘most favoured nation’ outside the EU, and vice-versa, this would still leave the UK in a relatively disadvantaged position compared to the tariff-free relations of EU members amongst themselves. In addition, the WTO has no provisions for the free movement of labour, and has made only modest progress in the liberalization of trade in services – an area of key importance to the UK.
In these circumstances, of course, the UK would no longer be constrained by the EU’s own common external trade policy and agreements, or by the need to adhere to common EU regulations over a whole range of factors of production and exchange, and so more freely than it could under any of the other models it could pursue close economic relations with countries outside Europe. Clearly, however, whatever benefits and new opportunities this might bring, the freedom to do so would be at the cost of accepting significant competitive disadvantage within the European market place.
iv. Customized Membership
If Britain votes to remain, we have seen that the deal negotiated between the British government and the European Council offers an unprecedented variant of differentiated integration. Unilateral in initiative, bilateral in negotiation and conclusion, yet, with the important exception of the exemption from ‘ever closer Union’, multilateral in content and outcome, it offers a new form of customized membership. Its distinctiveness, however, lies less in what it does and more in what it may portend. On the one hand, the UK remains signed up to the vast majority of the vast EU legal acquis it was already committed to prior to the negotiation of the deal; and - to repeat - most of the new commitments entered into in the deal apply generally rather than to the UK alone. On the other hand, the exemption from ‘ever closer Union’ appears to anticipate a different attitude to future forms of integration, posing as a standing reservation in areas where the UK does not share the ambitions of other Member States.
How sustainable is such a settlement? One can envisage a number of alternative lines of development. One possible trajectory involves a hardening of this framework of semi-detached, customized membership for the UK. While still officially ‘in’ rather than ‘out’, a pattern might emerge whereby the standing reservation of the UK was regularly invoked, and where it became less involved with the European project across a range of policy areas. If this were the case, the result might begin to resemble the Swiss, a la carte version of the exit model discussed above. Formally speaking, the UK would be both more constrained by its existing obligations and in a better position to exercise a bargaining voice over new initiatives if, unlike Switzerland, it remained ‘in’ rather than ‘out’. In practice, however, a repeated pattern of opt-outs might lead to mutual distancing – a drift towards a position where expectations of the UK’s productive participation in the on-going project of integration were scaled downwards on either side.
Alternatively, the UK’s continuing membership, and the multilateral nature of most of the concrete new measures contained in the deal, might allow for its gradual re-integration into a fuller membership role. A ‘Yes’ vote might mark the end, or at least the temporary disappearance, of a viable exit option in British politics. It might in turn signal the re-emergence of a more pro-European approach, and the consignment of the ‘ever closer Union’ exception to the status of purely symbolic legislation.
A third option would see the UK’s exceptionalist initiative neither as confirmatory of its outlier role, nor as a short-lived gestural politics, but as a prompt for further multilateral treaty change. As the general nature of the pro tem solutions adopted under the British deal indicate, the issues raised in the Brexit context - the limits of sovereignty pooling, the reassertion of the powers of national Parliaments, the future of EMU, the response to mass migration and the scope of Social Europe - are hardly questions of interest to the UK alone. Broader concern with these matters, with the financial stability of the Eurozone and the willingness and capacity of the EU to absorb migratory flows from the South and East most likely to provide the catalyst, may lead to a more rounded resettlement initiative - perhaps involving the re-assertion of the Eurozone-centred variable geometry version of differentiated integration first mooted in reform discussions between the UK and the EU.
4. Concluding Remarks
The point of my remarks has been to show that, regardless of the verdict on June 23rd, the position of a post-referendum Britain is likely to be neither fully ‘in’ nor fully ‘out’, but somewhere ‘in-between’. In the first place, there will be the twilight zone of negotiations. In the event of either result, these are likely to be lengthy, uneasy and unpredictable. In the second place, the long-term models of UK re-engagement with Europe are in any case better understood as fluid points on a spectrum rather than as categorical alternatives. The future of European Union today is in many ways as uncertain as is the future of the UK within the European Union, but most of the architectural alternatives for our continent involve a significant degree of differentiated integration – a trend that is only reinforced by the continuing pressure from neighbourhood states to join the club and the consequent need to build intermediate structures of attachment. The choice for Britain is shaped perhaps as much by the availability and negotiability of these alternative models of differentiation as it is by its bald ‘yes or no’; conversely, the choice for Europe may be significantly influenced by the precedent set in the British case, both as the first state to formally contemplate exit, and what might be negotiable on the other side of exit, and as a trend-setter in the patterns and possibilities of differentiated membership.
Such a prospect of mutual influence might seem somewhat far-fetched. One of the more unfortunate symmetries of the Brexit debate, after all, has been the pattern of mutual indifference. The campaigners on either side have hardly considered the wider EU interests at stake, while the rest of the EU, at least until the end-game, has paid strikingly little attention to the insular British debate. Yet once the dust settles, other more immediate crises pass, and structural questions find their way back onto the European agenda, the Brexit debate and decision may assume a different meaning. Ironically enough, the very preparedness of the UK to think outside the box of uniform supranational integration, provided relations are not fatally poisoned by a corrosive Euro-cynicism on our side and/or an equivalent UK-cynicism on the European side, may allow our domestic experience to be influential and instructive in the reshaping of European integration over the decades to come.
Neil Walker is Professor of Public Law and the Law of Nature and Nations at the University of Edinburgh. An earlier version of this piece can be found on the Royal Society of Edinburgh’s Enlightening the European Debate website.
 European Council Conclusions, 19 February 2016, EUCO 1/16.
 Perhaps most notably, Boris Johnson on the occasion that he first declared for ‘No’ following the making of the British deal at the European Council meeting in February, though he quickly ruled out this option. See http://www.independent.co.uk/news/uk/politics/boris-johnson-performs-eu-u-turn-on-double-referendum-a6899516.html. Nevertheless, at the behest of Johnson himself and of others such as Michael Howard, the ‘Breturn’ option has continued to raise it head at various points in the campaign; see e.g., F. Mount, ‘Nigels against the World’ (2016) (38(10) London Review of Books 21-23.
 European Council Conclusions, 19 February 2016, EUCO 1/16. ‘The United Kingdom and the European Union’ para. 3(iii)
 The general ‘enhanced co-operation’ provisions in Arts 226-34 of the Treaty on the Functioning of the European Union (TFEU) are the best example of this approach in the present Treaty framework. However, they are concerned exclusively with the option of additional integration beyond the EU norm rather than opting–out from the norm or co-operating below the level of the norm. This restriction illustrates the awkward fit between the a la carte model and the prevailing ethos of EU integration mentioned in the main text.
 European Council Conclusions, 26-27 June 2014, EUCO 79/14.
 See e.g. R. Liddle, ‘The Risk of Brexit: Britain and Europe in 2015 (London: Rowman & Littlefield, 2015) ch.1.
 See e.g., D. Leuffen, B. Rittberger and F. Schimmelfennig, Differentiated Integration: explaining variation in the European Union (London: Macmillan, 2013).
 See e.g. F. Mount, ‘Nigels against the World’ (2016) (38(10) London Review of Books 21-23.
 At the moment, following the accession of Croatia as the EU’s 28th member in 2013, there are five officially recognised EU candidate countries – Albania, Macedonia, Montenegro, Serbia and Turkey, and two countries – Bosnia and Herzegovina – that have been promised candidate status in due course. This moving belt is closely tied up with the EU’s Stabilisation and Association Process (SAP) towards the Western Balkans.
 See e.g., J-W. Muller, ‘Europe’s Sullen Child’ (2016) 38)11) London Review of Books 3-5.