Retained EU law and assimilated law

Retained EU law

When the UK left the EU, the European Union (Withdrawal) Act 2018 (EUWA) saved EU rights and obligations and turned them into domestic law.

This huge new body of law was called ‘retained EU law’.

Powers in EUWA made modifications to retained EU law. This ensured that it continued to function when the UK left the EU.

For example, references in retained EU law to the European Commission were replaced with references to the secretary of state.

Retained EU law was interpreted as it had been previously:

• the case law of the Court of Justice of the European Union continued to be binding on UK courts
• the principle of the supremacy of EU law was preserved
• the relationship between different parts of the statute book remained as before

The general principles of EU law were also saved as an aid to interpret retained EU law.

Assimilated law

The Retained EU Law (Revocation and Reform) Act 2023 (REULA) made major changes to the law saved under EUWA.

The concept of ‘retained EU law’ was removed and relabelled ‘assimilated law’.

The principle of the supremacy of EU law was removed.

The starting point is that domestic law (whenever enacted) takes precedence over what was previously EU law. This is subject to certain exceptions, for example in data protection law.

REULA also:

• removed EU rights and obligations saved through section 4 of EUWA
• deleted the general principles of EU law
• gave powers to ministers to revoke, replace, restate, update, remove or reform assimilated law

In July 2025, the UK government published a report on the revocation and reform of assimilated law.

As of June 2025, assimilated law encompassed 6,911 instruments covering approximately 400 unique policy areas.

What this means for solicitors

There is little case law so far on the effect of REULA. The changes REULA has made to the statute book will emerge in the coming years.

These have the potential to be problematic.

For example, removing the principle of the supremacy of EU law may have unintended consequences and lead to a lack of legal certainty. This could also be the case for reversing the hierarchy between different parts of the statute book.

These changes may create difficulties across the vast number of policy areas which are regulated by assimilated law.

The changes may impact solicitors working in areas such as:

• environmental law
• consumer protection
• intellectual property
• employment law

What we’re doing

We will continue to review the effects of REULA closely to understand the potential impact on our members.

To share your views or experiences, email georgina.berriman@lawsociety.org.uk.

Our work so far

Summer 2023 – we met with other civil society organisations concerning the bill and engaged with parliamentarians as the bill moved through the House of Lords.

May 2023 – we welcomed the amendment removing the sunset clause, approved at report stage in the House of Lords on 15 May.

February 2023 – we briefed peers ahead of the bill’s second reading in the House of Lords.

January 2023 – MPs from across the political spectrum quoted our evidence in a House of Commons debate about the bill.

November 2022 – we submitted evidence to the Public Bill Committee outlining our thoughts on the legislation.

October 2022 – we briefed MPs ahead of the bill’s second reading in the House of Commons, based on concerns raised by several of our committees.

July 2021 – we responded to the Ministry of Justice’s consultation on departure from EU retained case law by UK courts and tribunals.