I have written before about whether triggering the formal Brexit process under Article 50 of the  Treaty on European Union requires legislation. My view is that, as a matter of law, the arguments around whether legislation is needed or whether the prerogative can be used are finely balanced, but that the better view is that legislation is not required. I have also argued that, in policy terms, the case for parliamentary involvement in or a referendum on any eventual Brexit deal is extremely strong.

Two recent posts on the UK Constitutional Law Association Blog return to the question of whether legislation is needed to trigger Article 50. John Adentire argues that triggering Article 50 would entail the removal of fundamental rights, and that the principle of legality therefore precludes the triggering of Article 50 other than through primary legislation. Meanwhile, Gavin Creelman contends that the question whether the prerogative can be relied on for the purpose of triggering Article 50 needs to be examined with reference to the decision in Thoburn v Sunderland City Council (a case that I have written about elsewhere). This post briefly responds to and challenges those arguments.


In Thoburn, Laws LJ distinguished between ordinary and “constitutional” legislation, arguing that the latter is immune from implied repeal and is subject to repeal only by “express” or “specific” provision. Laws LJ was clear in Thoburn that the European Communities Act 1972 is a “constitutional statute”:

It incorporated the whole corpus of substantive Community rights and obligations, and gave overriding domestic effect to the judicial and administrative machinery of Community law. It may be there has never been a statute having such profound effects on so many dimensions of our daily lives. The ECA is, by force of the common law, a constitutional statute.

Creelman argues that if we agree with Laws LJ that the ECA is a constitutional statute, then we must conclude that Article 50 cannot be triggered under the prerogative. That is so, he says, because the “reasoning in Thoburn suggests that the common law … gives protection to a broader idea of the constitutional settlement between the citizen and the state”, meaning that legislation governing that settlement is immune from implied repeal. The core of Creelman’s argument, then, is that the UK’s membership of the EU has — through the medium of the ECA — altered the domestic constitutional settlement, and that Thoburn “prevents this settlement from being significantly altered in the absence of express statutory authorisation”.

This, however, relies upon an overbroad reading of Thoburn. The principle laid down in that case is concerned with the conditions that apply to the repeal of constitutional legislation, exempting such legislation from implied repeal. However, as I have argued before, neither triggering Article 50 nor ultimately leaving the EU would entail implied repeal of the ECA. Indeed, Creelean acknowledges this:

[T]he ECA exists to give effect to the obligations imposed on the UK by the EU treaties as a matter of international law “from time to time”. Invoking Article 50 and leaving the EU would result in the UK ceasing to be subject to any such international obligations, and therefore in the ECA ceasing to have anything to give effect to. It would not, however, remove the ECA from the statute book or introduce any contradictory provision into domestic law, in the manner of an implied repeal.

It is difficult, therefore, to see how the “constitutional legislation” limb of Thoburn may be relevant. (I turn, below, to the “fundamental rights” limb.) It would only be relevant if, as Creelman argues, Thoburn renders the use of express provision in primary legislation a condition precedent to doing anything that would result in the adjustment of relevant constitutional arrangements. But in fact Thoburn is far more limited than this. As a restriction upon the manner of repeal of legislation, it is only relevant if existing legislation is being repealed by subsequent legislation. But that condition is plainly not fulfilled because, as already noted, the activation of Article 50 does not entail any form of repeal of the ECA. Thus the Thoburn principle is simply not relevant: since nothing is being repealed, the conditions that would apply if something was being repealed are beside the point.

Fundamental rights

Laws LJ also said in Thoburn — reprising views he had earlier advanced in R v Lord Chancellor, ex parte Witham — that the “express” or “specific” words requirement applies to the “abrogation of a fundamental right”. This principle, often referred to as the “principle of legality”, is well known and broadly accepted. Again, it is not clear that it clearly bites upon the Article 50 question. However, Adentire (with whom Creelman agrees on this matter) argues that it does. The argument here is that EU law supplies fundamental rights and that the principle of legality precludes those rights from being taken away save by express provision in primary legislation.

On the face of it, there is more mileage in this argument. For one thing, it applies whether or not the repeal — express or implied — of legislation is in contemplation. In the light of that, the argument advanced above — that the “constitutional legislation” limb of Thoburn is not engaged because triggering Article 50 does not entail any form of repeal of the ECA — does not similarly undermine an argument based on fundamental rights. Instead, the argument made by Adentire and supported by Creelman works whether or not any constitutional legislation is being amended or repealed, biting as long as fundamental rights are being removed. Nevertheless, there are difficulties with the fundamental rights argument.

The first difficulty is that triggering Article 50 does not in itself entail the removal of any rights, fundamental or otherwise. But even if that argument is rejected — on the grounds that, as Adentire argues, triggering Article 50 would open up “a real possibility” of the abrogation of EU-derived rights — the attempt to leverage the principle of legality runs into a second difficulty. That is so because the “fundamental rights” acquired via EU law are not the type of rights to which the principle of legality applies. The roots of that principle, which we find in cases such as Witham, lie firmly in the common law. That is not to deny that the content of the body of common law rights — and so the field of application of the principle of legality — can and may be influenced by international law, including EU law and the ECHR. For example, as Lord Reed put it in Osborn v Parole Board, the common law of human rights falls to be developed “in accordance with” Convention rights when appropriate. The possibility thus arises that the common law may acknowledge or absorb rights that initially found expression as ECHR or EU rights, but ECHR and EU rights are not necessarily also common law rights. And, crucially, is it common law constitutional rights upon which the principle of legality bites. Nor does the fact that EU rights are — in some sense, having acquired national legal force via the ECA — statutory rights bolster any argument concerning the principle of legality. Indeed, in Moohan v Lord Advocate, Lord Hodge (with whom Lord Neuberger, Lady Hale, Lord Clarke and Lord Reed agreed) took the view that rights — such as the right to vote — that find primary expression as statutory rights are thereby excluded from the category of common law constitutional rights.

It is therefore difficult to see how rights that derive from EU law would qualify as the type of fundamental rights upon which the principles set out in Thoburn, Witham and other relevant domestic cases bite. Indeed, if it is the case that the relevant principles apply only to common law rights, then the argument advanced by Adentire and supported by Creelman becomes highly problematic. On the one hand, some of the rights conferred by EU law may mirror fundamental rights acknowledged at common law. In those circumstances, the triggering of Article 50 would not place those rights at risk and eventual Brexit would not abrogate those rights, since they would continue to subsist at common law. On the other hand, EU law doubtless acknowledges rights that lack analogues at common law. But in respect of those rights, the principle of legality does not bite upon their removal or attenuation, because such rights are not, in the first place, rights that are recognised and protected by the common law constitution.

Concluding remarks

It is worth concluding by referring to the Supreme Court’s decision in the HS2 case (on which I have written here). In their joint judgment in that case (with which the other Justices agreed), Lords Neuberger and Mance moved beyond the approach adopted by Laws LJ in Witham in two key respects. First, they indicated that constitutionality may be a matter of degree rather than a binary question: that, for instance, some things might be constitutional in nature, but that some might be (my term) super-constitutional in nature. Second, in considering whether Article 9 of the Bill of Rights enjoyed constitutional priority over the European Communities Act 1972, the analysis of Lords Neuberger and Mance focussed upon the substantive constitutional importance of the relevant arrangements and principles, rather than upon the relative constitutional statuses of the two pieces of legislation at stake. This goes some way towards dissolving what is, to my mind, a problematic and artificial distinction between (on the one hand) constitutional legislation and (on the other hand) constitutional rights, values and principles.

All of which is significant when it comes to the question of Article 50. In particular, it suggests that if a Thoburn-based (but HS2­-glossed) argument concerning Article 50 were to fly, it would be necessary to move beyond arguments about the “constitutional” status of the ECA or even the “constitutional” nature of the governance arrangements that flow from EU membership. The real question would be whether any of the arrangements, values, rights or principles resulting from EU membership enjoy a status that is so fundamental — viewed through the lens of the common law constitution — as to immunise them against interference save by express provision in primary legislation.

Inevitably, the answer to that question is debateable. But, for my own part, I see little merit in the argument that anything flowing from EU membership enjoys the requisite form of fundamentality. EU rights that are also common law constitutional rights will remain available. EU rights that are not also common law rights are no concern of the common law constitution. And it is difficult see to see why any aspects of the EU legal system’s broader architecture — such as the primacy of EU law or the jurisdiction of the Court of Justice — should be regarded as fundamental from the perspective of the common law constitution. In a recent speech, Lord Neuberger said that Brexit “may well mean that the influence of EU law will be a 50-year blip on the near thousand years of the life of the common law”. The point perhaps appears flippant, but it contains an important grain of truth: that the practical legal and constitutional impact of EU membership should not be confused with the normative domestic constitutional value (or lack thereof) of the trappings and implications of such membership.