Brexit is effectively taking place on 31 December 2020. In preparation, the UK and the EU concluded the withdrawal agreement – which is underpinned by international law – in 2019. 

The teaching of international law is a key component of any modern law degree. In the second year at our law school, we teach a specific unit focusing on the legal relationship between the UK and EU. It builds upon previous skills introduced in effective legal research, using sources and legal writing.

Like any international agreement, no signing party can unilaterally amend or disapply the withdrawal agreement. Surprisingly, the UK government’s proposed internal market bill overrides parts of the withdrawal agreement that relate to trade with Northern Ireland. This is particularly puzzling because to avoid a hard border between Ireland and Northern Ireland, the latter would have to comply with the EU single market norms. 

To add to the confusion, there are voices in politics, academia, social media and others bringing legal and extra-legal arguments claiming a breach in international law by the UK and, conversely, the UK’s right as a sovereign state to do as it wishes.

To help our students better understand the impact that Brexit and the new internal market bill will have in the UK, we must stress the importance of looking at how the UK, international law and EU law are related; and to distinguish what is law from what is not.

Laws with a difference

EU law is a type of international law – that is, regional international law. Until recently, the EU had to do with its own (EU) law and 28 different national legal orders (the UK being one of these). With Brexit, the way in which this legal relationship operates will soon change for the UK.

International law is created by, and binding between, sovereign states (and international organisations). Treaty law is based on the principle of pacta sunt servanda whereby treaty obligations freely concluded by a state must be respected by that state. The term means that ‘agreements must be kept’ and, accordingly, obligations must be performed in good faith. States cannot invoke their national law as an excuse for failing to perform their treaty obligations towards other contracting states. 

An important point to note is that the status of international rules within the domestic legal order is determined by constitutional rules of the state. The internal effect of a treaty is a matter of national law. That is to say, it is up to each sovereign state to decide whether international law and national law are part of the same legal system, or two different legal systems. 

Furthermore, it is for each sovereign state to decide whether national law is superior or inferior in relation to international law. This decision is of utmost importance in cases in which rules in national law and international law contradict each other: which one will prevail? There are two answers to this question: monism and dualism.

These are contrasting philosophies that are vital to students’ understanding of international law in relation to Brexit – preparing them for the complexities of many cases they may see when they enter practice.

Monism affirms that international legal norms are, upon their ratification by the domestic government, part of the national legal order while preserving their international nature.

For dualism, national legal orders are separate orders from international norms. For international law rules to have a place in these national legal orders, they have to be made part of national law before they can become operational. The procedure on how to introduce these international law rules into the national legal system is determined by national institutions (for example, by an act of parliament). 

These international rules are then enforceable by courts as national law. Therefore, nothing can prevent dualist states from accepting the superiority of national law over international law. 

Supremacy

Things are more complicated in EU law. Internationally, sovereign states are bound by the treaties signed by their representatives (according to the Vienna Convention of the Law of Treaties, to which the UK is signatory). 

According to the principle of supremacy (or primacy), EU law has priority over the national legal order of member states. It means that when any EU rule applies in a given situation, the conflicting national norm should be set aside by the relevant judge. Although the principle of supremacy of EU law is not included in any EU treaty, the Court of Justice of the European Union has maintained the principle of supremacy of EU law over national legal orders.

This new bill is an attempt by the UK government to regulate trade within the country after leaving the EU. This document would have two fronts: internally, the aim is to avoid new barriers to trade in the UK, such as with Scotland; and externally, to act and be seen by other states internationally as a single unified market. 

One of the most controversial points of the new bill is that the ministers have powers to amend the implementation of the protocol on Ireland and Northern Ireland (included in the withdrawal agreement). In particular, part 5 section 45 clearly indicates that “certain provisions [will] have effect notwithstanding inconsistency or incompatibility with international or other domestic law”.

The UK government, as the representative of a sovereign state in international law, has the right to change its law. If that change in the internal legal normative results in a breach of international law it is a separate issue. 

As a signatory of the withdrawal agreement, the UK is bound by its content. It follows that if, by changing its domestic law (ie with the internal market bill), the UK does not comply with the withdrawal agreement, then there is a clear breach of an international law obligation previously agreed with the other signatory (the EU). (The question remains whether this is a good or bad political decision, a question that belongs to politics not law.)  

From the above, a dualist country like the UK is a sovereign state. Therefore, it is the prerogative of parliament (or the Queen in parliament) to decide when and how to incorporate international law into UK national law, when to reject it, disapply it or even to break it. 

Different from national legal orders, international law does not count with the means to enforce sanctions. However, it is worth noting that despite the lack of the legal enforcement of sanctions internationally, not to comply with one’s obligation affects the reputation of that given state.

In other words, it will remain to be seen whether other sovereign states would want to enter into international agreements with the UK, knowing it may not honour its previously agreed obligations.

The political decision may have ramifications. With this breach in international law, and Brexit taking place in the weeks to come, the situation may have a direct impact on other areas such as the bargaining power of Scotland and Northern Ireland; the future internal legal and political unity of the UK; territorial disputes such as the Falkland/Malvinas islands, Gibraltar, Northern Ireland; and many others. 

These ramifications may have a major influence on the way we practice and teach the key tenets of international law in years to come.  

Dr Jorge Emilio Núñez is a senior lecturer at Manchester Law School mmu.ac.uk

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