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02 Aug 2021

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The ‘rule of law’ is a phrase invoked often and elaborated rarely. At heart, it refers to the underpinnings which give the rules of law force and create a form of legal order. A critical distinction lies in how this is conceptualised in the domestic compared to the international context. Grasping this is essential to understanding the UK’s ongoing relations both with the EU and further afield.

In broad terms, the domestic model is conceptualised as operating on a hierarchy between law-giver and subject, whereas the international operates on a horizontal plane.

This is not an arcane academic debate, nor is it an issue of semantics with no purchase in the real world. Rather, understanding this structural difference between domestic and international legal systems is the master key which helps unlock many of Brexit’s most contentious issues.

The 18th century legal philosopher John Austin defined the domestic legal system as an order in which a distinct chain of command runs from the sovereign down the societal chain to the people. There is an enforcement structure embodied in institutions such as the police and the judiciary.

The international legal order has no such hierarchy (save for the human rights concept of Jus Cogens inapplicable here). Rather, a dwarf is as much a man as a giant – all states are sovereign equals. The horizontal structure of international law follows from this.

Rather than a legislative body authoring and enforcing rules from the top down, they are authored and maintained by the constituent members of international society – states.

Why does this matter? It matters because without the sort of enforcement system that individual citizens of a state enjoy at the domestic level, the international system is one that is broadly reliant on trust between states.

What then gives law force in this horizontal structure? The answer is deceptively simple, despite being closeted behind the intimidating lingua franca of international law. Pacta sunt servanda: agreements must be kept.

In absence of hierarchy, this legalistic Esperanto is the lynchpin of international law. It is built from the fundamental principle of sovereign equality.

I sense an objection. How can you say international law is horizontal if there are courts, such as the European Court of Justice and the European Court of Human Rights? Are these not hierarchically superior to states? Well, no. The reason again is deceptively simple.

A sovereign state must consent to these courts in order for jurisdiction to be established. The same principle applies to treaties such as the Withdrawal Agreement. For context, the hierarchical nature of the domestic legal system does not require such consent. Legal obligation flows from the top down.

Another potential objection: the EU is not a state, how can the principle apply? Indeed, the EU is not a state. But again, consent holds the key to unlock the answer.

The EU is an intergovernmental organisation: the same principle attaches to states acting collectively as they do individually. States have consented through myriad treaties to construct the EU as an entity as it currently exists.

In doing so, each has mutually consented for the EU to act internationally and upon the same principles. The very authority of the EU is built upon the consent of individual member states. As an international institution, it is a gift made available by the sovereign authority of its constituent members.

As Brexit illustrates, sovereign authority also means this consent may be withdrawn.

What purchase does an obscure Latin phrase and an elaborate ‘ok’ have in contemporary debates surrounding the UK and the EU? The answer lies in what Brexit was fought for. It was, after all, a battle voiced in the key of sovereignty. Whatever one’s opinion on this matter, the battle is over.

But if one is to concede this point, a counterpoint must also be realised: that is, to fight shy over what sovereignty requires once the battle has been won makes a mockery of the entire premise of Brexit and all those who fought both for and against it.

It may then be argued that sovereignty would have only been realised under a ‘no-deal’ scenario.

Again, this is not the case and consent once more unlocks why this is so. Sovereign authority would have allowed the UK to pursue such a course of action. But the UK freely consented to the Withdrawal Agreement. In doing so, the UK committed itself to observe its terms underwritten by the principle of pacta sunt servanda.

These two principles, consent and pacta sunt servanda are then bedrock principles of the international legal order. They are the foundations upon which the house of international law is built.

Pertinently, they are qualities that are themselves extensions of what it means to be sovereign. Sovereign authority and sovereign responsibility are then two sides of the same coin, to ignore this critical linkage devalues its worth.

But what relevance does this have? The furore prompted by Brandon Lewis’ comments that the UK was prepared to break parts of the Withdrawal Agreement in a ‘specific and limited way’ have been reignited by comments that the UK is prepared to unilaterally invoke Article 16. To be sure, both the UK and the EU have the right to invoke Article 16 and indeed both have flirted with the idea.

Yet as Clare Rice demonstrates, the intent behind the agreement was one anchored on the prior agreement to submit such concerns to a Joint Consultative Working Group. The more serious concern, though, are the calls to rip up the Withdrawal Agreement completely.

The effects of such ruminations run deeper than a mere breach of contract. They impinge upon the necessary degree of trust for orderly international trade relations across the board. Crucially, the aftereffects live longer in the international public consciousness than any incumbent government could wish to.

The UK must then demonstrate its fidelity to these foundational principles of the international legal order. Principles which are themselves the embodiment of the ‘full English breakfast’ variety of sovereignty that Brexit was fought for.

The need for a robust international reputation is then crucial, both for the UK’s relations with the EU and in the paths it seeks to clear and progressively build upon with other states and trading blocs. In order to chart such a course successfully, to make Brexit a success, our consent must necessarily mean our word.

Flirting with breaking international law, even if only in a ‘specific and limited way’, chips away at this moral authority. To disregard it completely would shatter any claim to moral propriety.

To succeed as an independent sovereign nation, it is then imperative that the UK demonstrates the willingness to keep to agreements once made. Pacta sunt servanda.

By Oliver Pierce, a research student and teacher of political thought and international relations at Cardiff University. 

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