Parliamentary Sovereignty in the United Kingdom: Pre- and Post-Brexit

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The exit of the United Kingdom (UK) from the European Union (EU), commonly referred to as Brexit, was one of the country’s most divisive political decisions of the last decade. The United Kingdom European Union membership referendum held on June 23rd, 2016, effectively commenced a transition period that ended on December 31st, 2020, officially securing the country’s independence from the EU. The proponents of Brexit contend that leaving the Union was a moral duty of both the Parliament and the people of the UK. It has long been claimed that the EU substantially undermined the country’s parliamentary sovereignty and that post-Brexit Britain will finally be free to make its laws and regulations. However, there is an opinion that post-Brexit parliamentary sovereignty is mostly illusory. This report will consider some of the relevant court decisions made during the country’s EU membership and argue that a return to full parliamentary sovereignty is unfeasible at the moment.

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Defining Parliamentary Sovereignty

Parliament sovereignty is the supreme principle of the UK Constitution. In the UK, Parliament has the ultimate lawmaking power, can create, enact, and abolish any law, and no written constitution limits its powers (Russell, 2020). The principle of sovereignty has its origins in the Crown and Parliament Recognition Act 1689 (Spencer, 2019). According to the act, “the superior constitutional authority is located in Westminster Palace rather than Buckingham Palace” (Greene, 2018). Thus, the act effectively limited the Monarch’s power as the head of state, bestowing the ultimate legislative power upon the Parliament.

Nevertheless, it is erroneous to assume that the power of Parliament is unlimited and is not bound by any laws. According to the UK Parliament (2021), sovereignty is limited by the devolution of legislative power to the Scottish and Welsh Parliaments, both of which can create and enact laws in Scotland and Wales, respectively. The Human Rights Act 1998 limited the power of the Parliament by outlining the fundamental rights and freedoms that cannot be violated by any legislation (UK Parliament, 2021). Similarly, the establishment of the Supreme Court in the UK in 2009 also limited the power of the House of Lords (UK Parliament, 2021). As the Parliament enacted these limitations to its sovereignty, it can be argued that the legislative body retained its autonomy as outside forces did not challenge it, and the legislative body could repel these changes. However, the UK’s entry into the EU in 1973 is also viewed as an obstruction of the supreme principle of sovereignty. Therefore, it is essential to discuss whether the EU impeded the parliamentary autonomy and authority and how they are affected following Brexit.

Parliamentary Sovereignty before Brexit

To understand how the parliamentary sovereignty of the UK was affected by the EU, the country’s entry into the Union should be examined. The European Communities Act 1972, repealed on December 31st, 2020, was the legislation that allowed the country’s entry into the EU and ensured “EU law supremacy over UK national law” (The Institute for Government, 2020). Thus, to join the Union, the UK Parliament was forced to incorporate the EU Constitutions into its own, diluting the domestic legislature. Specifically, the 1972 act resulted in the EU legislation directly affecting Britain, without the UK Parliament passing that legislation to be effective in the country (The Institute for Government, 2020). Moreover, the act allowed some EU legislation to be enacted in the UK by primary parliamentary or secondary legislation in the form of statutory instruments (The Institute for Government, 2020). Meanwhile, all UK laws passed after 1973 had to comply with the EU requirements.

Overall, it can be asserted that the European Communities Act 1972 challenged and restrained the parliamentary sovereignty of the UK. It demanded the legislation passed by the Parliament to comply with the requirements of the Union and allows for the legislation of the outside forces to take precedence over the country’s legislation. Furthermore, the act demanded that the national courts override national laws if they were found to be incompatible with the EU legislation (McConalogue, 2019). Similarly, Costa v Enel (1964) court case that occurred before the UK entered the European Union ruled that if a national law contradicts the EU law, it must be repealed (Ringeisen-Biardeaud, 2017). Thus, the European Communities Act 1972 allowed the courts to challenge and abolish any national laws that they had no power to do before as the Parliament alone had the ultimate legislative power. Such decisions as the devolution of legislative power to the Scottish and Welsh Parliaments and the establishment of the Supreme Court can be viewed as the decentralization of the Parliament’s power. Whereas the entry into the EU resulted in the Parliament being subservient to the Union’s legislation.

Furthermore, the dissolution of the EEC and the formation of the EU brought new challenges to the sovereignty of the UK Parliament. The Treaty of Lisbon that formed the EU specified the division of power between the Union and its member states, effectively affording the EU absolute authority within the defined “exclusive competencies” (McConalogue, 2019). As a result, along with other EU members, the UK lost all legislative power over such sectors as the common commercial and monetary policies and the customs union (McConalogue, 2019). In addition, specified “shared competencies” bestowed equal power of the EU, the UK, and other member states in such areas as social policies, economic and social cohesion, and the internal market, among others (McConalogue, 2019). Thus, the EU’s Treaty of Lisbon blocked the UK Parliament’s ability to enact legislation in several sectors, challenging its sovereignty.

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Several court cases illustrate the parliamentary sovereignty of the UK being challenged by its EU membership. For example, in Litster v Forth Dry Dock and Engineering Co Ltd 1990, the House of Lords ruled that legislation construed to conform with a European Directive should be given a purposive construction (Dorani, 2020). Thus, the courts expressly ruled in support of the EU legislation over the UK legislation and moved away from supporting the UK Acts of Parliament. Similarly, the 1991 Factortame II Secretary of State for Transport case found the UK’s parliamentary Merchant Shipping Act 1988 contradicted the Article 43 EC and should, therefore, be overruled (Dorani, 2020). Thus, the House of Lords was forced to abolish the Act of Parliament to comply with the EU regulations. Overall, it can be asserted that the country’s EU membership substantially impacted the sovereignty of the UK Parliament.

Parliamentary Sovereignty after Brexit

The UK’s exit from the EU marked a new era for the country. However, the question of parliamentary sovereignty and whether the country will be able to secure the autonomy it once had remains open. Therefore, it is crucial to consider the EU Withdrawal Act 2018 and consider its effect on the UK and the country’s legislative body. The act repeals the European Communities Act 1972 and adopts all EU laws and regulations made since 1973 into the UK legislation under the EU retained law legislation (The Institute for Government, 2018). In addition, it grants ministers the power to change those legislations to ensure they are appropriately worded for their enactment in the UK (The Institute for Government, 2018). Thus, despite the country not being a member of the EU, many European laws and regulations are likely to remain unchanged and be in force on the territory of the country. However, considering Brexit, the UK parliament will have more power over those laws and will be able to abolish them if needed.

The retainment of the EU laws raises the question of whether the newfound autonomy of the UK Parliament is, in fact, illusory. According to Mac Amhlaigh (2019), the UK is predicted to retain the constitutional pluralist features in its relationship with the EU, somewhat undermining its quest for sovereignty. It can be argued that full autonomy is difficult to achieve in modern realities as the global interdependence and the incapacity of states to address global problems on their own are ever-increasing (Mac Amhlaigh, 2019). In addition, the Scottish and Welsh Parliaments will be able to retain the majority of its powers, “except in areas where UK ministers will use statutory instruments to say otherwise” (The Institute for Government, 2018). Thus, the UK’s legislative authority will remain decentralized, and the country is unlikely to regain the parliament sovereignty of the 1972 constitutional model. It can be argued that new agreements of the UK with the EU, as a non-member state, will also limit some of its legislative power.


In summary, the UK’s exit from the EU was the most significant political decision of the country in the last decade. Although there are plentiful evidence in legislation and relevant court cases that the EU law prevailed over the national law, it remains unclear whether parliamentary sovereignty will be fully secured after Brexit. At the moment, UK Parliament autonomy is primarily illusory, with many EU laws retained and the legislative power remaining decentralized. However, it can be assumed that pre-EU sovereignty will not be achieved due to the increased global interdependence.

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Dorani, S. (2020) ‘The primacy of EU law over national law: Great Britain’s response’, Political Reflection Magazine, 6(24), pp. 25-39. Web.

Greene, A. (2018) ‘Parliamentary sovereignty and the locus of constituent power in the United Kingdom’, International Journal of Constitutional Law, 18(4), pp. 1166-1200.

Ringeisen-Biardeaud, J. (2017) ‘“Let’s take back control”: Brexit and the Debate on Sovereignty’, French Journal of British Studies, 22(2), pp. 1-17. Web.

Mac Amhlaigh, C. (2019) ‘Back to a Sovereign Future?: Constitutional Pluralism after Brexit’, Cambridge Yearbook of European Legal Studies, 21, pp. 41-58. Web.

McConalogue, J. (2019) The British constitution resettled: Parliamentary sovereignty before and after Brexit. Springer.

Russell, M. (2020) ‘Brexit and Parliament: The anatomy of a perfect storm’, Parliamentary Affairs, 74(2), pp. 443-463. Web.

Spencer, T. (2019) The sovereignty of Parliament, the rule of law, and the High Court of Parliament, UK Constitutional Law Association. Web.

The Institute for Government (2020) European Communities Act 1972, The Institute for Government. Web.

The Institute for Government (2018) EU Withdrawal Act 2018, The Institute for Government. Web.

UK Parliament (2021) Parliament’s authority, Web.

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"Parliamentary Sovereignty in the United Kingdom: Pre- and Post-Brexit." DemoEssays, 25 Aug. 2022,


DemoEssays. (2022) 'Parliamentary Sovereignty in the United Kingdom: Pre- and Post-Brexit'. 25 August.


DemoEssays. 2022. "Parliamentary Sovereignty in the United Kingdom: Pre- and Post-Brexit." August 25, 2022.

1. DemoEssays. "Parliamentary Sovereignty in the United Kingdom: Pre- and Post-Brexit." August 25, 2022.


DemoEssays. "Parliamentary Sovereignty in the United Kingdom: Pre- and Post-Brexit." August 25, 2022.