Does it show a strength or a weakness in the constitution that the Miller decision was reached on the basis of principles said to be centuries old?

Despite the unprecedented nature of the Miller case (the first time the Supreme Court Justices had all sat together to hear an appeal), there is little unprecedented about what they decided: Parliament is sovereign; only Parliament, and not the executive, can effect changes to the law; and that is particularly so where the changes proposed are to the constitution.

But the fact that the appeal was determined on the basis of rules that were said to have been forged centuries before the current dispute perhaps raises its own questions. There are three aspects that may be worth dwelling on: the actual basis of the decision; the role of Parliament in controlling the executive; and what, if anything, the decision tells us about Parliament’s position in the constitution.

The prerogative

The scope of the remaining prerogative powers was generally agreed, and it was uncontroversial that conducting foreign relations, including making and breaking treaties, was one such prerogative (that being a “basic principle of our constitution”: para 194, per Lord Reed). So the question for the court was twofold: (a) did the 1972 Act somehow curtail that prerogative in relation to withdrawal from the EU (the Government argued it did not and thus the power was available); and (b) if exercising that prerogative would result in a change to domestic law, did Parliament need to authorise its use (Ms Miller et al argued that it would, so Parliament did).

As a starting point, the majority (led by Lord Neuberger) and the minority (led by Lord Reed) disagreed on what inference, if any, could be drawn from the 1972 Act about continued membership of the EU. Lord Reed held that: “The Act imposes no requirement, and manifests no intention, in respect of the UK’s membership of the EU” (para 177). The majority, on the other hand, held that the very enactment of the 1972 Act saw Parliament endorse the UK’s membership of the EU (paras 77 and 82) and, having given effect to that, Parliament could not have intended to leave the executive with the power to withdraw without involving Parliament in that decision (para 90).

Whether the 1972 Act curtailed the prerogative power to withdraw from a treaty was answered by the majority under reference to the domestic effect of such a notice (in other words, the answer to (b) inevitably resolved (a)). For the majority, it was a fundamental rule of the constitution that the prerogative does not allow the executive to change the law (para 50). As giving notice under article 50 would inevitably lead to leaving the EU, and membership of the EU brought with it unprecedented constitutional change, the law would be changed and thus it was a step that had to be sanctioned by Parliament (paras 81-82). That conclusion was reinforced by an orthodox application of the sovereignty of Parliament (para 90).

That being so, Lord Reed’s attempt to show that the 1972 Act was not conditional on continued membership of the EU (para 197), and that the Act did not qualify the prerogative in relation to the conduct of foreign relations (para 204), became nothing to the point: withdrawal would effect significant domestic constitutional change and that must be a matter for Parliament, not the executive. Subsequent legislation did not help the Government: the power claimed by the Government would have to be expressly conferred by Parliament, and the Government conceded that no such language had been used (para 112).

Parliament and the executive

Prerogative powers are anomalous in the sense that they permit executive action, but Parliament has had no say in them. In 2003, the House of Commons Public Administration Select Committee suggested that should no longer be acceptable to Parliament or the people (Taming the Prerogative: Strengthening Ministerial Accountability to Parliament, Fourth Report of Session 2003-04, HC 422, para 61). But one issue that arises from the case is Parliament’s role in supervising the exercise of these powers. Whilst the majority opinion answers the narrow question that was before the court, it is perhaps Lord Carnwath’s dissenting opinion that provides a better idea as to what should follow as the process of negotiation gets underway.

As Lord Carnwath explained, the process that comes after article 50 notice is given “will be conducted by the executive, but it will be accountable to Parliament for the course of those negotiations and the contents of any resulting agreement” (para 259). Much of his judgment explains the important role that Parliament plays in supervising the executive and holding it to account (para 252, for example). That should be the primary mechanism by which the executive is held to account (as opposed to the court: see also para 240, Lord Reed). That takes us to Parliament’s position and how it approaches that task.


Arguably, Parliament has a bit of an identity crisis: what is its proper role where the people have given their view on a question that Parliament put to them? How does it represent the minority who disagreed? How far can Parliament go to question the executive’s interpretation of the result? How does it respond to an executive that has no electoral mandate (beyond the referendum result) for the policy it now seeks to implement? What, if any, role can the House of Lords play (no doubt acutely aware of its unelected character)?

At least some of those problems are of Parliament’s own making: it has never completed House of Lords reform (which it started in 1911), and it chose not to legislate for the consequences of the referendum result. But perhaps all of this is symptomatic of the underlying theme of the judgment: we have an unwritten, flexible, pragmatic constitution (para 40), which answered its biggest case in decades by applying principles which are said to be centuries old. That strikes of nothing having really changed: it is odd that a constitution that evolves in a “pragmatic” way answers difficult questions by reference to apparently fixed principles.

Take one example: “Parliamentary sovereignty is a fundamental principle of the UK constitution, as was conclusively established in the statutes referred to in para 41” (para 43). Refer back to para 41 and we find the Bill of Rights, the Act of Settlement, the Claim of Right and the Acts of Union. Each predates the establishment of the Parliament for which they “conclusively established” its powers. But was the die really cast at the end of the 17th century? Before the advent of universal suffrage? Before referendums? Before modern government that dominates the elected chamber? Why has that principle proved immune to the otherwise “flexible” and “pragmatic” nature of the constitution? Sir Stephen Sedley explained how the idea of incontestable, inalienable and universal rights changes over time (Sedley, “Human Rights and the whirligig of time” (2016) 20 Edin LR 1). If those rights are not immune to the passage of time, why are some constitutional rules?

So the case was resolved by an orthodox application of orthodox principles, but it is surprising that the orthodox was so uncritically accepted. Parliament looks out on a much changed country, but is reassured by the Supreme Court that nothing has really changed. Perhaps the constitution is not as flexible as we have all believed? Perhaps it is, in truth, fairly brittle? If it is, that is a cause for concern, given the increasing strain placed upon it. So perhaps the main question that arises from the judgment is, why have things not changed? And the fact that they apparently have not is perhaps more a cause for concern than it is a source of comfort.


The Author
Paul Reid, advocate, Ampersand stable. This article is based on a paper delivered at the Ampersand seminar
 “The Constitution After Brexit and where we go now”, held on 6 February 2017.
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