A contract still refers to retained EU law, yet the term has changed. What is retained EU law? It is EU-derived law that the European Union (Withdrawal) Act 2018 saved into UK law, now officially labelled assimilated law.
The label is only part of the story. This guide separates the original conversion of EU rules from the later renaming and reform, and the wider context is in the hub on eu citizens rights after brexit.
How the Withdrawal Act created retained EU law
The aim was continuity: rules that businesses and individuals already relied on kept working in the UK legal system instead of lapsing on departure.
Gowling WLG sets out the main mechanics. Section 2 saves EU-derived legislation, and section 3 incorporates certain direct EU legislation into UK law. The term itself is defined in section 6(7) of the Act. Direct EU legislation matters here because it applied without a separate UK statute. The route that produces such rules is covered in the explainer on how are EU laws made.
The Act was drafted around exit day, 11 pm on 31 January 2020. The transition period moved the practical cut-off. Travers Smith describes retained EU law as starting life as a snapshot of all EU law in force at 11 pm on 31 December 2020, called IP Completion Day in the legislation. The Brexit timeline shows how those two dates relate.
Retained EU law and assimilated law side by side
The two terms are often treated as rival categories. They describe the same body of EU-derived law at different stages, as the comparison below shows.
| Point | Retained EU law (Withdrawal Act 2018) | Assimilated law (2023 Act) |
|---|---|---|
| Label | Retained EU law | Assimilated law, with the new terminology effective from 1 January 2024 |
| Starting point | A snapshot of EU law in force at 11 pm on 31 December 2020 | The same category of EU-derived law, relabelled and open to ministerial change |
| Supremacy of EU law | The principle applied | The principle was removed; domestic law takes precedence, with exceptions such as data protection |
| Court of Justice case law | Continued to be binding on UK courts | Little case law yet on how the 2023 Act changes this |
The comparison draws on the Law Society’s overview of retained EU law and Travers Smith’s ten key questions.
Misunderstandings about the renaming
The Retained EU Law (Revocation and Reform) Act 2023 is the source of most confusion. Its name suggests mass deletion, but its effect on the label and on existing rules is narrower.
- Renaming is not repeal. The Law Society records that the retained EU law label was removed and relabelled as assimilated law. Travers Smith notes that much of this body of law remains exactly the same as it was before Brexit. A rule that was retained EU law in 2023 does not disappear because its category now has a new name.
- Old documents rarely need a wholesale rewrite. The same Travers Smith note says it should generally not be necessary to change all references to retained EU law in existing contracts. The new terminology took effect from 1 January 2024. Documents drafted from then on can use the new term, and older wording still points to the same body of law.
- The label is not a verdict on any single rule. Whether a particular EU-derived provision, right or obligation is retained, is a matter of statutory interpretation. Calling something assimilated law tells a reader its category, not whether it has since been changed.
Revocation and reform under the 2023 Act
The 2023 Act’s practical force lies in the powers it gave ministers. According to the Law Society, it gave powers to ministers to revoke, replace, restate, update, remove or reform assimilated law. Reform is therefore a continuing process carried out rule by rule, not a single deletion event.
The size of the task explains why. The Law Society reports that, as of June 2025, assimilated law encompassed 6,911 instruments covering approximately 400 unique policy areas. That breadth is why the effect varies so much by sector: a business in one policy area may see little change while another faces amended rules.
Where to find what has changed
In July 2025 the UK government published a report on the revocation and reform of assimilated law, as the Law Society notes. For anyone asking which laws have been revoked or reformed, that report is the document to consult for a particular area. Travers Smith adds that the government has set up a searchable database of retained EU law, a practical starting point for locating an individual instrument.
Because the 2023 Act is recent, interpretation is still settling. The Law Society observes that there is little case law so far on the effect of the Act, so conclusions about borderline provisions should stay cautious.
EU case law, supremacy and UK courts
The question of whether EU case law still binds UK courts has a different answer depending on the period. Under the Withdrawal Act, the case law of the Court of Justice of the European Union continued to be binding on UK courts. The CJEU is the EU’s own court, and its rulings had shaped how EU rules were read before exit.
The 2023 Act altered the underlying hierarchy. The Law Society states that the principle of the supremacy of EU law was removed, and that the starting point is that domestic law, whenever enacted, takes precedence over what was previously EU law. Exceptions exist, and data protection is one the Law Society names. The practical lesson is that a conflict between a later UK statute and an older EU-derived rule is no longer resolved in favour of the EU-derived rule by default.
Northern Ireland
The UK-wide picture has one notable carve-out. Travers Smith points out that the Northern Ireland Protocol provides that certain aspects of EU law continue to apply there. A discussion of assimilated law that ignores this can mislead readers whose business or residence is in Northern Ireland.
Reading a rule in practice
Anyone trying to work out where a specific EU-derived rule now stands can follow a short sequence.
- Identify the instrument. Note whether it is a UK regulation implementing EU requirements or direct EU legislation incorporated by section 3 of the Withdrawal Act.
- Confirm it is retained. Treat this as a question of statutory interpretation, using the definition in section 6(7) as the anchor.
- Look it up. Use the government’s searchable database to locate the instrument, then check the July 2025 report for revocation or reform in its policy area.
- Check precedence. If a later domestic statute covers the same ground, domestic law generally prevails, subject to exceptions such as data protection.
- Consider Northern Ireland. Where the matter touches the Protocol, certain EU law may still apply.
Anyone relying on a rule for a legal decision should check the current text, because ministerial powers mean the position can change after any summary is written.
Frequently asked questions
| Question | Answer |
|---|---|
| Is assimilated law a different body of law from retained EU law? | No. Assimilated law is the new label for the same category of EU-derived law, introduced by the Retained EU Law (Revocation and Reform) Act 2023. |
| Did the Withdrawal Act make all EU law part of UK law? | No. It saved EU-derived legislation under section 2 and incorporated certain direct EU legislation under section 3, rather than adopting every EU measure. |
| Has retained EU law been abolished? | No. The 2023 Act relabelled it and gave ministers powers to change it, and much of it remains as it was before Brexit. |
| Does EU supremacy still apply? | No. The principle of the supremacy of EU law was removed, so domestic law takes precedence, with exceptions such as data protection. |
| When did the assimilated law terminology take effect? | Revised wording came into force on 1 January 2024. |