Why was it introduced (political and sociological context)?
The European Union Act 2011 introduced restrictions on the ratification of treaties amending or replacing the European Union’s founding treaties and on UK approval of certain decisions under those treaties. Following the signing of the Treaty of Lisbon in 2007, Parliament passed the European Union (Amendment) Act 2008, which provided for the Treaty to take effect in UK law. A proposal for a UK-wide referendum on the Treaty was defeated in the House of Commons by 311 votes to 248. The 2011 Act emerged against this political backdrop and responded to calls for greater parliamentary and public control of future transfers of power to the EU.
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What was the aim of the Act (legal context)?
The aim of the Act was primarily to strengthen UK procedures and safeguards for agreeing to EU treaty changes and certain decisions. It also affirmed that directly applicable and directly effective EU law was recognised in the UK by virtue of domestic legislation.
What main changes did it make to the law?
The primary change introduced by the Act was the requirement for a referendum before the UK could ratify certain treaties or approve certain decisions transferring power or competence to the EU. This became known as the referendum lock. The Act did not require a referendum for every treaty amendment. Other decisions required approval by an Act or by motions in both Houses, depending on the provision that applied.
The 2011 Act replaced most of the earlier approval requirements in sections 5 and 6 of the European Union (Amendment) Act 2008. Section 18 was declaratory. Directly applicable and directly effective EU law continued to be recognised through the European Communities Act 1972 or another Act requiring its recognition. Section 18 did not require a new Act of Parliament for each directly applicable or directly effective EU measure or alter the priority that EU law had under the 1972 Act. The Supreme Court explained this effect in R (Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5 at [60]–[67].
Key Sections
Section 2 required a statement to be laid before Parliament under section 5, approval by an Act of Parliament and satisfaction of the referendum condition or the exemption condition before a treaty amending or replacing the Treaty on European Union (TEU) or the Treaty on the Functioning of the European Union (TFEU) could be ratified. The referendum condition required a referendum throughout the UK, or the UK and Gibraltar, and a majority in favour. The exemption applied where the approving Act stated that the treaty did not fall within section 4. Section 3 imposed similar requirements on decisions under the simplified revision procedure in Article 48(6) TEU and provided a limited additional exception for certain changes which the approving Act stated were not significant in relation to the UK.
Section 4 set out the types of change that could trigger a referendum. Accession of a new member state, codification of an existing practice or provision applying only to other member states did not by itself trigger one. Section 5 required a ministerial statement, including an opinion on whether section 4 applied. Sections 6 to 10 provided for approval of other decisions under the treaties. Sections 11 to 13 dealt with the referendum franchise and related matters, including the Electoral Commission’s role. Part 2 approved a protocol enabling the UK to take up an additional European Parliament seat. Section 15 approved the protocol, and section 16 and Schedule 2 dealt with filling the seat.
2026 update
The European Union (Withdrawal) Act 2018, Schedule 9, repealed the European Union Act 2011 in stages. Sections 1 to 13, 14(1) and 15(1), and Schedule 1, were repealed on 4 July 2018. The remaining provisions, including section 18, were repealed at the end of the transition period on 31 December 2020. The 2018 commencement regulations preserved the validity of acts and omissions in relation to matters previously approved or exempted under the 2011 Act.
The referendum on EU membership on 23 June 2016 was held under the separate European Union Referendum Act 2015. The United Kingdom left the EU on 31 January 2020. The European Communities Act 1972 was repealed on exit day, subject to savings for the transition period.
After the transition period, the 2018 Act preserved EU-derived domestic legislation and incorporated specified direct EU legislation. The Retained EU Law (Revocation and Reform) Act 2023 revoked specified legislation and removed the general domestic rule of EU law supremacy for this body of law, subject to statutory exceptions. The retained law that survived became known as assimilated law from 1 January 2024.
Separate provision is made for the domestic effect of the Withdrawal Agreement under section 7A of the 2018 Act. This includes citizens’ rights and applicable EU law under the Windsor Framework for Northern Ireland. Those arrangements operate under the Withdrawal Agreement and the 2018 Act.
Last updated: 12 November 2026
