Earlier today, the Secretary of State for Exiting the European Union, Stephen Barclay MP, posted a tweet saying that he had “signed the legislation setting in stone the repeal” of the European Communities Act 1972 (ECA). (The ECA is the UK statute that gives effect to EU law in the UK’s domestic legal system.) He went on to assert that this is a “landmark moment” because it “underlines that we are leaving the EU on 31 October”.

At best, this is misleading. All that Barclay has done is to bring into force section 1 of the European Union (Withdrawal) Act 2018 (EUWA). It says that: “The European Communities Act 1972 is repealed on exit day.” However, the effect of bringing section 1 into effect is decidedly modest. Most importantly — and, given the wording of the section, obviously — bringing that provision into force does not immediately repeal the ECA: rather, it only repeals it on “exit day”. “Exit day” is currently defined by section 20(1) of the Act as 31 October. But other provisions in section 20 enable the definition of “exit day” to be amended if the date of the UK’s departure from the EU changes under EU Law. Indeed, this is precisely what happened when extensions to the Article 50 period were agreed between the UK and the European Council in the spring.

There is no legal reason why this could not happen again — and, crucially, bringing section 1 of the EUWA into force makes absolutely no difference to this point. Whether section 1 is in force or not, it only produces legal effects from “exit day”. It follows that if, for example, Parliament were to require the Government to seek, and if the European Council were to grant, a further Article 50 extension, the definition of “exit day” could be further amended in order to ensure that the ECA was repealed only with effect from the new, later date of the UK’s departure from the EU.  This, in turn, means that — contrary to his claim — the Brexit Secretary has not “set in stone” the repeal of the ECA. The EUWA explicitly contemplates that “exit day” can be changed in order to enable it to be aligned with the actual date of the UK’s departure from the EU.

This leads on to a further, and critical, point. “Exit day” is a concept whose relevance liis wholly in domestic law. It is the date on which various provisions of the EUWA swing into action, in order to ensure that the domestic legal consequences of leaving the EU are appropriately managed — including by converting vast swathes of EU law into domestic law. However, the domestic definition of “exit day” has no bearing whatever on when and whether the UK leaves the EU. That is a matter that is governed exclusively by EU law. Similarly, whether the ECA is in force or not has no bearing on whether or when the UK leaves the EU — although if the UK were to repeal the ECA before leaving the EU, it would immediately be in breach of EU law. From this, it follows that whether the ECA is repealed or not is neither here nor there when it comes to whether or when the UK leaves the EU. All it is relevant to is whether, for as long as it remains a member, the UK does or does not comply with the legal obligations under the EU Treaties that are binding on it in international law.

All of this demonstrates that the legal significance of bringing section 1 of the EUWA into force is extremely limited. It does not “set in stone” the repeal of the ECA, because the legal meaning of “exit day” can be changed and the date of the ECA’s repeal deferred. It does not prevent the UK Government from seeking an Article 50 extension. It does not prevent Parliament from legislating to require the UK Government to seek an Article 50 extension. It does not prevent the European Council from granting an extension if the UK Government asks for one, whether of its own volition or at Parliament’s insistence. And it does not prevent Parliament, if it so wishes, from legislating to revoke the UK’s notification under Article 50, thereby stopping the Brexit process in its tracks. The politics, of course, are another thing. But any suggestion that ECA repeal has been “set in stone”, or that this somehow locks in 31 October as the inevitable date of the UK’s departure from the EU, is wrong as a matter of law. ECA repeal, and Brexit itself, are no more “set in stone” today than they were in the spring, when “exit day” was twice redefined in domestic law and the Article 50 period was twice extended as a matter of EU law.