Article 50 and international treaty-(un)making: An Overview

The recent High Court judgment on whether the Government can notify, under article 50 TEU, withdrawal from the EU unilaterally without recourse to Parliament raises significant constitutional issues.

In particular, it required consideration of the overarching principle of Parliamentary sovereignty, the extent of the residual nature of the Crown’s Prerogative and the effect of the enactment of the 1972 European Communities Act.

The High Court found that the Government did not have a “prerogative” right to notify withdrawal without Parliamentary approval.

The full judgment is here:

From an international law point of view, there are four points which I think are worth highlighting.

First, “Parliament remains sovereign and supreme, and has continuing power to remove the authority given to other law by earlier primary legislation. Put shortly, Parliament has power to repeal the ECA 1972 if it wishes” (para 21)

Secondly, as the High Court noted at paragraph 30: “Another settled feature of UK constitutional law is that, as a general rule applicable in normal circumstances, the conduct of international relations and the making and unmaking of treaties on behalf of the United Kingdom are regarded as matters for the Crown in the exercise of its prerogative powers”.

Thirdly, the Government had argued that, in accordance with the above, there is a “proper sequencing of the respective functions of the Crown and of Parliament”, namely “the withdrawal treaty would in any event have to be approved by Parliament by way of the negative resolution procedure in the [Constitutional Reform and Governance Act 2010] before that occurred; if it contained provisions requiring application in domestic law, primary legislation would also need to be introduced to allow that” (para 76(7)). This reflects the old Ponsonby convention dividing powers between the Government on the international plane and Parliament domestically.

Fourthly, notwithstanding the validity of this approach generally, in relation to the European Communities Act however “Parliament intended EU rights to have effect in domestic law and that this effect should not be capable of being undone or overridden by action taken by the Crown in exercise of its prerogative powers” (para 94).

It is thus right to identify the judgment as a fundamental reassertion of Parliamentary sovereignty, but equally it is not as sweeping as might be thought – the judgment relates to EU law, not to treaty-making (and unmaking) generally.

There is some suggestion that a similar argument might apply to the Human Rights Act / European Convention on Human Rights but this must be conjecture at this stage.

Of course, the judgment is to be appealed to the Supreme Court, and from an international law perspective, I would suggest keeping an eye on three things:

1) how will the Supreme Court deal with the argument that the moment of article 50 notification does not per change British law, but that this occurs later at the point of withdrawal (and by repeal of the ECA)? This was the finding of a Northern Ireland court on a similar (though not exactly identical) claim. How far notification – in contrast to the later withdrawal treaty – is itself perceived as affecting domestic law will be fundamental to how the Supreme Court determines the appeal. In part, but only in part, the question of the revocability of article 50 is relevant here.

2) how will the Supreme Court approach the earlier case of ex parte Rees Mogg, that the High Court distinguished, but which had said that “When Parliament wishes to fetter the Crown’s treaty-making power in relation to Community law, it does so in express terms” or arguably at least by necessary implication? Even if this is true, does it apply to withdrawal, in contrast to situations of “alter[ing] or add[ing] to the EEC Treaty”?

3) in short, will the Supreme Court agree with the High Court that the ECA and the incorporation of EU law into British law displace the traditional rules (see above paras 30 and 76(7))?

These are only a small number of the questions that the Supreme Court will need to consider.

Professor Duncan French