The notion that concerns (rooted in Euroscepticism) about sovereignty can be addressed by means of legislation asserting the sovereignty of the UK Parliament appear to be gaining increasing traction. In a debate in the House of Commons 3 February 2016, the Prime Minister, David Cameron, said that although the sovereignty of Parliament was already assured, it is “something I’m keen to do even more on, to put beyond doubt that this House of Commons is sovereign”. This appears to echo an argument made in 2015 by Daniel Hannan MEP. Writing on the ConservativeHome website, Hannan argued that the UK Parliament should enact a “Sovereignty Act” to reassert its supremacy in the face of European Union law and the European Convention on Human Rights. Writing that EU law “overrides the law of our own democratic institutions”, his proposed solution to this perceived problem is that the UK should take a step that “requires no one else’s permission”:

We could amend Sections 2 and 3 of the 1972 European Communities Act to reassert the supremacy of Parliament. We could make clear that, in any conflict between Westminster and Brussels, Westminster has the final word.

Whether the UK Parliament should have the final word is a question of perspective. I do not propose to engage with that question here. However, analysed as a matter of law, Hannan’s proposal reveals three fundamental misconceptions that go to the heart of the debate concerning the UK’s relationship with both the EU and the ECHR. Given that that debate is likely to run for some time, it is as well to be as clear as possible about the legal groundrules.

First, then, Hannan’s argument is misconceived because it presupposes that parliamentary sovereignty has been given away and now needs to be reclaimed. Since the first of those things has not happened, the second need not and cannot happen. Hannan points out, correctly, that in the Factortame case the Appellate Committee of the House of Lords (since replaced by the Supreme Court) applied EU law in preference to conflicting provisions in a UK statute. However, this does not imply that Parliament is not sovereign. To the contrary, the House of Lords made it clear that it was applying EU law because that is what UK law — in the form of the European Communities Act 1972 — required.

Not only does Factortame establish that parliamentary sovereignty was not given away; subsequent case law stipulates that it cannot be given away. As Laws LJ put it in the Thoburn case: “Being sovereign, [Parliament] cannot abandon its sovereignty.” And if Parliament did not and cannot give away its sovereignty, it cannot and logically does not need to reclaim it from Brussels. A Sovereignty Act would therefore be legally pointless because parliamentary sovereignty can already be asserted simply by stipulating in given legislation that it is to prevail over any incompatible EU law.

Second, Hannan argues:

Since the early 1990s, most of the national supreme courts of the other EU states, including France’s Conseil d’État and Germany’s Bundesverfassungsgericht, have pushed back, taking opportunities to proclaim their own supremacy. But Britain, lacking a written constitution, has no chance to do so. We are therefore arguably in the weakest position, vis-à-vis the EU institutions, of all the 28 member states.

This, too, is incorrect; it confuses the absence of a written constitution with the absence of a constitution. The UK lacks the former; it does not lack the latter. The point is well illustrated by the Supreme Court’s recent judgment in the HS2 case. It establishes that the effect given to EU law in the UK, and hence the extent to which EU law may prevail over incompatible domestic law, is to be determined by interpreting section 2 of the European Communities Act 1972. And, the Supreme Court said, section 2 falls to be interpreted in the light of fundamental domestic constitutional principles. In the absence of clear language to the contrary (and none exists in section 2) the courts will assume that Parliament did not intend, when enacting section 2, to permit EU law to prevail over basic constitutional values. In HS2 itself, the Supreme Court indicated that this approach could be used, for example, to prevent EU law from overriding constitutional values reflected in the Bill of Rights 1688-9. It is therefore not the case that the absence of a written constitution means that EU law can ride roughshod over fundamental domestic principles.

Third, Hannan conflates two things that bedevil the debate concerning not only the relationship between UK and EU law, but also the debate about the Human Rights Act 1998 and British membership of the European Convention on Human Rights. The two things in question are the sovereignty of Parliament as a domestic-legal institution and the sovereignty of the United Kingdom as a State in international law. Hannan is right to say that Parliament, being sovereign, is at liberty to assert its sovereignty by enacting a Sovereignty Act (although, as we have seen, doing so would be legally meaningless). Crucially, however, asserting sovereignty in this way or in other ways — by, for example, legislating in breach of EU law or the ECHR — would not alter the fact that, as a matter of international law, the United Kingdom, as State, is bound by its obligations under the EU Treaties and the ECHR.

It follows that the problem which Hannan perceives cannot be unilaterally resolved by adopting a domestic statute. To suppose that it can reveals a parochial myopia which fails to acknowledge the reality of the UK’s position in international law. Whether enshrining such thinking in legislation makes political sense is, of course, a different matter entirely. But it is important, as the debate about Europe heats up, to be clear that the sort of difficulties perceived by commentators such as Daniel Hannan cannot be legislated away by Westminster. If they are to be addressed at all, they must be tackled by reference to the UK’s treaty obligations, not by the sort of legislative tinkering to which a “Sovereignty Act” would amount.