The European Union (Withdrawal) Act 2018 encodes the mechanism for UK withdrawal from the EU.

But given that it required agreement from the EU (did it), does it also have a treaty component, or correspondent in EU law?

1 Answer 1


The European Union (Withdrawal Act) 2018 is not a treaty, and is primarily concerned with necessary modifications to UK domestic law so that:

  1. The European Communities Act 1972 (i.e. the Act which generally allowed the translation of EU law into UK domestic law in the first place) was repealed.
  2. Existing domestic law derived from the above would generally remain in force by default
  3. There was a clear mechanism for the issuance of secondary legislation to fix any holes or weirdnesses this left (e.g. shifting responsibility from EU regulatory bodies to a domestic equivalent).

Due to mutual mistrust between the government and parliament it also required parliamentary approval for any withdrawal agreement.

I'm not aware of any direct EU equivalent, nor do I understand any to be necessary. The EU treaties had already been written to allow the EU membership to change, so generically apply to member states rather than to specific named parties. As such nothing implies that EU law, or its rights or duties would continue to apply to an ex-member.

In general, the UK has traditionally taken a very dualist approach to international law. That is to say, international law is taken to be a matter for the government, while only applying domestically if Parliament said it did. As such, there is no mechanism for the EU to directly interact with any Act of Parliament, although the government in power could be placed in a very difficult position by an Act which wasn't in line with its treaty commitments. To some extent this had been beginning to change, with judges beginning to make some reference to international human rights laws.

  • Thank you. The act encodes a leaving date (top of page 21) that presumably needed to be agreed/set in EU legislation? Or not?
    – 52d6c6af
    Sep 12, 2019 at 14:33
  • 2
    @Ben The leaving date only applies at the UK end, with a mechanism for Ministers to change it (subject to Parliamentary approval) also enacted (see point 4 on page 22). In theory nothing totally solid to prevent the UK using a different date from what the UK and the EU Council agree for an article 50 extension (i.e. "the day and time that the Treaties are to cease to apply" to use the language from the act), but practically that's really, really unlikely.
    – origimbo
    Sep 12, 2019 at 14:46
  • The last paragraph is a bit misleading. The UK may like to think that international law only applies in the UK if the UK parliament says so, but the ECJ has made it very clear that EU rules apply in the UK regardless. This is one of the reasons why Brexiteers argued to "take back control". However, human rights are not affected by Brexit, as those fall under the ECHR and that is much broader than the EU.
    – MSalters
    Sep 12, 2019 at 22:48
  • @MSalters your criticism of the last paragraph doesn't make any sense - the UK approach is entirely that - the ECJ approach is not the UK approach?
    – user19831
    Sep 15, 2019 at 11:48

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