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Important Research Achievements
[2017] Brexit and Its Impact on the UK’s Plural Legal System Brexit and Its Impact on the UK’s Plural Legal System
  • National Taiwan University Law Journal, 46 (2017): 1017-1114.


This paper discusses the legal problems and constitutional challenges caused by Brexit and its impact on the UK’s plural legal system. The UK has been a member of the EU since 1973 and has had to adopt all EU law, which by January 2017 comprised close to 19,000 items of EU law, constituting nearly 13% of UK law. EU law therefore adds to and enriches the UK's plural legal system. The main objective of Brexit is to “take back control” over legislative, judicial, budgetary and immigration sovereign powers, among others. Brexit has significant implications for UK parliamentary sovereignty, citizens’ rights, constitutional order, the plural legal system and the future UK-EU relation. Accordingly, Brexit is an important topic of legal complexity, political sensitivity and constitutional significance.


Core Issues

On 23 June 2016 the United Kingdom held a referendum on exiting the European Union. The Leave side won, with 51.9% of the votes, to the surprise of international onlookers. Brexit has already given rise to many legal problems. In particular, whether or not the notification to leave the EU had to be given prior authorization through legislation; the main legal issues involved in the Miller case triggered by Brexit; and how to solve the UK’s internal procedural problems for the Brexit notification? How are the UK and the EU going to conduct the Article 50 negotiations? What scope will EU laws have within the UK after it withdraws from the Union? What impact will the withdrawal from the Union have on the rights of British citizens? What are the main contents of the EU Withdrawal Bill? And what will the UK-EU relationship be like after Brexit? All these questions require a thorough study because they have enormous impact on the future UK-EU relationship and also for the British pluralistic legal system.


Major Findings

The major findings include:


  1. The rights of UK and EU citizens will be greatly affected by Brexit, for instance in the areas of immigration and residence, social welfare, free movement of persons, EU-UK trade and market access, etc;
  2. The 2017 Miller case confirmed that the UK government legally needed Parliamentary authorization to formally initiate the Article 50 procedure of the TEU;
  3. The 1972 ECA provides that EU law has direct effect and supremacy over UK law, and that the EUCJ’s rulings take precedence over UK courts, thus limiting Parliamentary sovereignty;
  4. Because of the ECA’s legal force as a constitutional Act, it cannot simply undergo “implied repeal” like other laws, for which the principle operates that new laws supercede previous laws; the ECA’s abolition requires a new constitutional Act of the same legal status to be passed by Parliament;
  5. The UK government will adopt an EU Withdrawal Bill to repeal the 1972 ECA on exit day. This will firstly take back control over UK laws and secondly, it will preserve EU laws’ effect in the UK on and after exit day, to avoid serious legal gaps and uncertainty in post-Brexit;
  6. Brexit will strongly affect the UK’s plural legal system, including the relationships between EU and UK law and between English and Scottish law; the biggest political risk post-Brexit is the possibility of a second Scottish independence referendum being triggered by Brexit;
  7. Article 50 TEU includes two different things: an agreement for exiting the EU and an agreement on the future relationship between the UK and the EU. In theory, if the UK has not achieved an agreement on exiting the EU within two years, then the UK will still automatically exit the EU on 29 March 2019; and
  8. Brexit will also result in a loss for EU law because it will reduce diversity and innovation within the EU legal system.




The accession to and exit from the EU are both decided by the UK. The direct applicability and supremacy of EU law in the UK’s legal system arises originally from the ECA 1972. In this context, the UK may certainly introduce an EU Withdrawal Bill to repeal the ECA 1972, to take back legal control from the EU. This conforms with  the UK’s traditional principle of parliamentary sovereignty, in the same vein as Mencius’s saying that: “If it was I who elevated it, then it is I who can also demote it.”What the UK has “elevated” are the state systems of “parliamentary sovereignty, constitutional tradition, legal culture and lifestyle and the independence of these things”. Even though “taking back control” of these prized items has led to Brexit, the UK does not regret it. Brexit also imposes a great loss on the EU and will weaken the EU’s plural legal system.

Brexit is a great challenge for both the UK and the EU. A soft Brexit or a hard Brexit, cooperation or confrontation, whichever one, it will affect the solidarity and success of the future UK-EU relationship. Yet, through disruptive innovation, the UK and the EU could transform the Brexit storm into competitive cooperation, turning a crisis into an opportunity, and building a new relationship in the future. As Shakespeare said: “What’s past is prologue.” This paper suggests that the UK and the EU must conduct rational negotiations and conclude a comprehensive FTA, in order to ensure continued cooperation and development in the plural legal systems of both the UK and the EU.


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