Since writing this post, I have written a longer piece examining the the constitutional implications of the UK’s membership of, and departure from, the European Union, with particular reference to the principle of parliamentary sovereignty. An overview of the paper can be found here; the full text can be downloaded here

That the United Kingdom’s Parliament is sovereign is a — perhaps the — fundamental principle of British constitutional law. Yet the supremacy of European Union law — meaning that it takes priority over conflicting laws enacted by individual Member States — is a basic principle of the EU’s legal system. These two propositions appear to stand in stark contrast to one another: they seem to imply competing, and ultimately contradictory, claims as to ultimate legal authority, at least in areas to which EU law applies. This, in turn, raises the question whether the UK’s membership of the EU (for as long as that membership persists) means that the sovereignty of Parliament is qualified by EU law.

One of the twentieth century’s greatest British public lawyers, the late Professor Sir William Wade, argued that the answer to that question is affirmative. He contended that the UK’s entry into the EU had triggered a constitutional ‘revolution’, whereby British judges had transferred their allegiance from Parliament to the EU as the ultimate lawmaker for the UK. In fact, Wade went further, arguing that parliamentary sovereignty is not merely suspended for as long as the UK remains a member of the EU, but that parliamentary sovereignty has been extinguished (albeit that on Wade’s view ‘Brexit’ could, but not necessarily would, reignite the notion of sovereignty). It was in that way that Wade sought to explain the landmark judgment of the Appellate Committee of the House of Lords in the Factortame case, in which part of an Act of Parliament was ‘disapplied’ on account of its incompatibility with EU law.

That such a momentous step was taken in Factortame is, on the face of it, grist to the mill of those who contend that sovereignty has been ceded to Brussels. Yet Wade’s analysis — and the dramatic consequences that it implies — is problematic. For one thing, it is incompatible with the way in which Lord Bridge — the only Law Lord in Factortame to consider this point in any detail at all — explained the judgment. He argued that any limitations upon its sovereignty implied by EU membership had been accepted ‘voluntarily’ by Parliament when it enacted the European Communities Act 1972. The implication was that Parliament is at liberty to permit EU law to prevail over its own enactments. The flip side of that coin must be that if Parliament chooses not to permit EU law to have that effect — either by repealing the 1972 Act or asserting the priority of only certain pieces of domestic legislation over conflicting EU law — then it is free to do so. Indeed, Parliament has indicated, albeit in somewhat cryptic terms, that this is its own understanding of the position: section 18 of the European Union Act 2011 stipulates that EU law has effect in the UK only because Parliament, by enacting the 1972 Act, has allowed it to.

This, however, raises a further question. If the priority enjoyed by EU law over UK law exists because of an Act of Parliament, what does this mean for parliamentary sovereignty? In particular, does it mean that Parliament is not sovereign while the UK is a member of the EU, albeit that that loss of sovereignty has come about because it is what Parliament wanted? Such an argument would raise difficulties of its own, not least because on any orthodox understanding of the sovereignty principle, limiting its own powers is — paradoxically — the one thing that Parliament cannot do. As Laws LJ put it in the Thoburn case: ‘Being sovereign, [Parliament] cannot abandon its sovereignty.’ How, then, to account for the view that Parliament has somehow managed, via the European Communities Act 1972, to elevate EU law above its own enactments?

… whatever limitation of its sovereignty Parliament accepted when it enacted the European Communities Act 1972 was entirely voluntary.

— Lord Bridge, Factortame (No 2)

That question goes unanswered in the Factortame case, but at least the beginnings of an answer to it can be found in the subsequent decisions of the Administrative Court in Thoburn and the Supreme Court in the HS2 case. Those judgments develop the idea that the 1972 Act — along with certain others — is a ‘constitutional statute’, meaning that it prevails over other legislation unless such legislation explicitly overrides the 1972 Act. This means that the efficacy conferred on EU law by that Act holds good, including in the face of legislation that is incompatible with EU law, unless such legislation expressly says otherwise. Parliament is, then, sovereign in the sense that it remains capable of overriding EU law by revoking or qualifying the priority accorded to EU law by the 1972 Act. But the courts will only take Parliament to have done that if it makes its intention crystal—that is, explicitly—clear. On this analysis, the degree to which EU law has priority over Acts of Parliament turns upon the interpretation of Acts of Parliament, and so the matter remains ultimately within Parliament’s control.

Where, then, does this leave us? If EU law is supreme, can Parliament be sovereign? The answer is ‘yes’. Parliament can insist that domestic legislation — either generally, or in respect of particular Acts — is to prevail over EU law. This follows because the default primacy enjoyed by EU law in the UK is itself attributable to an Act of Parliament — that is, the 1972 Act — and Parliament remains capable of amending, overriding or even repealing that Act. In Miller, the majority’s analysis reinforces the view that Parliament has remained sovereign throughout the UK’s membership of the EU, albeit that the majority also suggests that while EU law has effect in the UK thanks to the 1972 Act, EU law can also (and should) be thought of as a “direct”, “independent” and “overriding” source of domestic law. The Miller majority fails to make clear how its analysis relates to the position adopted by the Supreme Court in the HS2 case.

The general conclusion — that Parliament remains sovereign, the EU supremacy principle notwithstanding — is subject to an important caveat: that while, as a matter of domestic law and politics, parliamentary sovereignty can be exercised in spite of the EU supremacy principle, it does not qualify or limit that principle. This seems to take us back to our original problem: that the sovereignty of Parliament and the supremacy of EU law appear to be fundamentally incompatible. But this is not in fact so. Their reconciliation can be achieved by recognising that they operate in different legal spheres, albeit that those distinct spheres may, and do, come into contact with one another. Parliament is sovereign as a matter of UK law. In contrast, the EU supremacy principle is binding upon the UK as a matter of EU, and so ultimately international, law. So while the UK as a State is bound by its Treaty obligations to abide by EU law, this does not in itself require parliamentary sovereignty to be denied as a domestic legal principle.

Ultimately, then, Parliament retains the domestic legal authority to make whatever laws it pleases, even if such laws conflict with EU law. But, as a matter of EU and international law, doing so may place the UK as a State in breach of its obligations under the EU Treaties. The upshot is that, for as long as the UK remains a Member State of the EU, parliamentary sovereignty still exists, but it is unlawful — as a matter of EU and international law — for sovereignty to be exercised in ways that are incompatible with EU law.

This post forms part of my 1,000 words series. I have written in more detail about the implications for parliamentary sovereignty of the UK’s membership of the EU elsewhere, in particular in an article published in the Northern Ireland Legal Quarterly concerning the Thoburn case, and in a paper published in the European Constitutional Law Review on the Supreme Court’s HS2 decision.