Solving the autonomy conundrum: Can the UK avoid a hard border in Northern Ireland without subjecting itself to EU judges?

Armin Cuyvers

LERU Brexit Seminar

LERU Brexit Seminar



Solving Northern Ireland, the main obstacle to an orderly Brexit, is primarily a political challenge. EU law, however, imposes some legal limits that make this political challenge even harder. One of the less-known but potentially deal-breaking limits is the autonomy of EU law. Briefly put, autonomy can force the UK to either accept a hard border in Northern-Ireland or continued jurisdiction of the EU Court of Justice (CJEU) post-Brexit. This is because (1) any Brexit deal that guarantees sufficient free movement to prevent a hard border needs to incorporate EU law, and (2) any agreement that incorporates EU law must grant the ultimate say over how this EU law is interpreted to the CJEU.

This blog explores a possible legal solution to this autonomy conundrum. It argues that sufficient legal wiggle room might be created within autonomy by balancing it against other, equally valid general principles of EU law. Such a modified interpretation of autonomy might leave sufficient legal space for a Brexit compromise that is acceptable for the EU and the UK, whilst sufficiently safeguarding the EU legal order.

The legal context: the Northern-Irish deadlock

A hard border is deemed an unacceptable risk for the Irish peace process. The EU and the UK have therefore committed to preventing a hard border at all costs. To avoid the risk of a hard border, the Commission has included the so-called ‘back-stop’ in the current draft withdrawal agreement. This back-stop essentially means that, after Brexit and transition, Northern-Ireland remains part of the EU internal market and customs union, unless another solution is found that avoids the need for a hard border. This back-stop, which creates a border within the UK, has so far been rejected by the UK. To convince the EU to drop the backstop, however, the UK has to come up with an alternative. In short, if it wants to avoid either ‘loosing’ Northern-Ireland or a hard Brexit, the UK needs to find a future relationship that safeguards free movement of goods to such a level that borders become superfluous. Getting such a far reaching future relationship past sufficient factions of the conservative party, the DUP and a significant portion of UK voters will already be quite the political challenge. The political feasibility of such a far reaching relationship, however, would become even more limited if, due to autonomy, it would come with the additional cost of continued ‘subjection’ to EU law and EU judges.

Autonomy of EU Law and the obligatory jurisdiction of the CJEU

Autonomy means that EU law is self-referential: EU law decides how EU law works, when it applies and what its says. Autonomy forms the very foundation of EU law, including other famous principles as direct effect and supremacy. For the EU, therefore, autonomy is not just another legal principle. Autonomy is the Alpha and Omega of EU law, and any threat to autonomy is considered a threat to the very survival of the EU legal order. For many EU lawyers, therefore, surrendering autonomy equals surrendering the Temple mountain.

One key element of autonomy is that the CJEU must retain the final word on the application and interpretation of EU law. Consequently, autonomy is violated where the final say on EU law is taken away from the CJEU. This could, for example, happen where the interpretation of EU law is given to another international court, national court or arbitral panel which cannot ask preliminary references to the CJEU.

The challenge for Brexit is that the CJEU guards autonomy like a tiger its baby cub. It has been especially militant its most recent autonomy judgment in Achmea: the CJEU must retain the final word even if there is only a very small risk that a court or arbitral panel may, indirectly, be called upon to rule on an issue of EU law. Using the UK’s Chequers proposal, the next section shows how it seems impossible to safeguard sufficient free movement to prevent a hard border without triggering the Achmea hair-trigger, requiring continued CJEU jurisdiction post-Brexit.

Checking Chequers: why May’s proposal requires UK submission to the CJEU

The Chequers proposal, developed in the White Paper, aims to prevent a hard border by safeguarding free movement of goods (or ‘frictionless trade’ if you prefer). The UK firstly proposes a ‘free trade area for goods, including agri-food’. The EU and the UK would maintain a ‘common rulebook’, meaning the UK parliament would copy-paste most EU legislation on goods and agri-food.

Second, the UK proposes a ‘Facilitated Customs Arrangement’ (FCA). This essentially means that the UK would collect EU import duties and VAT on any goods that enter the UK and are then moved to the EU. The UK would use as yet non-existent ‘technology’ to trace which goods remain in the UK, and which goods are shipped onwards to the EU.

Together, the UK argues, the free trade area and the FCA remove any need for border infrastructure. The UK proposals, however, have been rejected by the EU as politically unacceptable and legally unworkable. The key point here, however, is not the feasibility of Chequers as such. The key point is that Chequers, even though it does not yet go far enough to prevent borders, already affects autonomy, and therefore requires CJEU jurisdiction post-Brexit. After all, Chequers requires the UK to de facto apply EU rules on goods, VAT and customs. These rules must, moreover, be interpreted the same as in the EU to ensure free movement.

Chequers itself, however, only provides for a limited role for the CJEU. Disputes are primarily settled via a Joint Committee, or via an arbitration panel if the Joint Committee cannot reach agreement. The Joint Committee would be able to ask preliminary questions to the CJEU, but only where both the EU and the UK agree to do so. The UK could thus prevent referrals. The arbitral panel would also receive the authority to refer questions to the CJEU, although Chequers does not specify how questions from the arbitral panel would be admissible under EU law or if the panel would ever be under an obligation to refer a question. An additional problem may be that ordinary UK courts would not receive the power to refer preliminary questions to the CJEU, even though many cases on the application of EU-based rules would probably end up before ordinary UK courts.

Although it forms an important step, and significantly softens the original UK red line on CJEU jurisdiction, Chequers does therefore not sufficiently respect the autonomy of EU law. This also means that a potential Chequers 2.0, which would go far enough to prevent hard borders, would be even more in need of sufficient CJEU jurisdiction to respect the autonomy of EU law. As the CJEU may be asked to provide a legal ruling on the agreement on the future relationship, and as the CJEU has proven that it is not afraid to reject painstakingly negotiated treaties, this is not a minor problem. Failing to respect autonomy could sink a Brexit agreement.

At the same time, even the current Chequers proposal already stresses UK politics close to, or maybe even beyond, its breaking points. Insisting that the UK accepts even more CJEU jurisdiction post-Brexit than under Chequers might well prove a bridge too far.

At his point one can of course argue that the UK should simply face up to the consequences of its own choice. Leaving the EU means borders. If the UK wants to avoid these borders, it needs to accept EU laws and CJEU supervision. At the same time, one could wonder if EU law should not be more constructive. Should EU law stick to an absolute interpretation of autonomy, despite widespread criticism of the militant interpretation of autonomy in Opinion 2/13 and Achmea? In light of this criticism, and the common interest in avoiding a loose-loose Brexit, the last section suggest one potential way of softening autonomy, and creating more legal space for Brexit.

Towards a mature form of autonomy: the balancing approach

So far, the CJEU seems to apply autonomy as an absolute rule: any agreement that undermines EU autonomy automatically violates EU law. The CJEU itself, however, also held that autonomy is not a rule but a general principle of EU law. And contrary to rules, principles can be balanced against other principles. In Schmidberger, for example, the CJEU balanced the principle of free movement against the freedom of expression and the freedom of assembly, also applying the principle of proportionality.

As autonomy is a principle, why not balance it against other principles and apply proportionality? Obviously, great weight should thereby be accorded to autonomy, as the foundation of the EU legal order. At the same time, largely hypothetical or minute risks to autonomy will rarely lead to the demise of the EU legal order. Such minute risks, therefore, can and should be weighed against the costs of enforcing absolute autonomy. An absolute stance may have been necessary in the early days, when the EU needed to establish itself. It no longer seems necessary, and perhaps even counterproductive, today. The EU has become a mature legal order, which must also recognize the legitimate interest of the other legal orders on which it rests ad depends.

Following a balancing approach, the CJEU could first of all balance the principle of autonomy against other general principles at stake in Brexit. These could include the principle of sincere cooperation, the duty to respect the national identities of (leaving) Member States, the effective right of Member States to leave the EU in an orderly fashion as recognized in Article 50 TFEU, respect for the British national democratic process under Article 2 TEU and respect for British procedural autonomy. Secondly, the CJEU could apply the principle of autonomy in line with the principle of proportionality. This means, amongst other things, that the costs of rigidly enforcing autonomy should be weighed against the benefits and that it must be asked if there are less far reaching ways of sufficiently protecting the EU legal order than demanding full CJEU jurisdiction. Might a limited risk to autonomy not be worth it, if it could enable a stable and constructive future relationship between the EU and the UK? For under a balancing approach, a more limited jurisdiction for the CJEU, one more in line with the Chequers proposal, might be found compatible with the autonomy of EU law.

Obviously the suggestion above requires an evolution in the case law, and one which goes against the trend since Opinion 2/13 and Achmea. The limited outlines provided also leave many questions open For example, the risk of slippery slopes should be avoided, also bearing Poland and Hungary in mind. Nevertheless, the suggestions provided here do build on solid precedent. Two brief examples may provide a proof of principle. Firstly in the context of supremacy. The CJEU has generally taken a very absolutist approach to supremacy. In principle, EU law trumps all national law, including national constitutions. Nevertheless, the CJEU has implicitly balanced supremacy against other principles, such as national procedural autonomy. In Kapferer, for instance, the CJEU accepted that final judgments from national courts need not be reopened, even if they do violate EU law. Although the CJEU does not expressly admits it, it thereby weighs legal certainty and national procedural autonomy against supremacy, with supremacy loosing. Secondly, in Kadi the CJEU initially stresses how fundamental rights form the very foundations of the EU legal order. Ultimately, however, the CJEU allows Kadi to remain listed on the EU sanctions list for three more months in violation of these very same rights. Again implicitly, the CJEU thereby weighs the ‘very foundations of the EU legal order’ against the more pragmatic risk that Kadi might indeed be involved in financing terrorism. The pragmatic considerations apparently won. If supremacy and fundamental rights, which form the very foundation of the EU legal order can be balanced against other principles and interests, then so can autonomy.


As EU law stands today, the autonomy of EU law forms (yet another) obstacle to solving Brexit. Considering the existing criticism on the strict interpretation of autonomy by the CJEU, and considering the horrendous damage that a hard Brexit would cause, however, Brexit might be seized as an opportunity to soften the EU concept of autonomy. As an additional benefit, such a softening would also increase the legal space for international trade agreements with dispute resolution mechanisms, including CETA.

Obviously, the softening proposed goes against the trend in the case law. It also asks EU lawyers, myself included, to ease up on one of our most sacred EU principles. Less than six months removed from a cataclysmic Brexit cliff, moreover, might be the right time to start thinking outside the legal box, on both sides of the channel.


Armin Cuyvers
Leiden University

Dr Armin Cuyvers is Associate Professor of European Law at the Europa Instituut of Leiden University. In addition to EU constitutional law and theory, he specializes in the free movement of complex services, anti-terrorist sanctions and the interaction between the national, EU and UN legal orders in combatting terrorism.

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