The Leave campaign has argued that membership of the EU limits the sovereignty of Parliament. But is this true? And what does it mean to be "sovereign"? 

In advance of June's referendum on the UK's membership of the European Union, both sides have set out several different types of argument supporting their respective positions. On the Remain side, the economic argument (i.e. that we would be poorer as a nation and worse off individually should the UK leave) has been most prominent. On the Leave side, the debate has centred primarily around immigration. Do we have control of our borders? Is immigration-driven population growth unsustainable? Does immigration have an adverse impact upon social cohesion?

Underpinning both sides of the debate however is the underlying issue of sovereignty. Put simply, has membership of the European Union reduced or limited the ability of the United Kingdom to determine its own laws? Or does membership of the European Union mean that we are subjected to laws passed by EU institutions imposed upon us without our consent?

To answer this question, it is important to first ask what "sovereignty" actually means.  To be considered sovereign typically requires that a governing body (in this case, Parliament) has the full right and power to govern itself without any interference from outside sources and bodies. Having defined what sovereignty means in conceptual terms we can then ask ourselves: is the UK Parliament sovereign?

The doctrine of Parliamentary sovereignty within the UK is long standing, having its origins in the 17th Century following the Glorious Revolution which commenced the transfer of power from the Monarch to the elected Parliament. Parliamentary sovereignty has often been characterised by constitutional scholars as comprising the following principles: (1) that Parliament can make whatever laws on whatever topic it so wishes, (2) that Parliament has no power to bind a future Parliament and (3) that a valid act of Parliament cannot be challenged by the courts. By fulfilling each of these criteria, it is clear that such a body would have the full right and power to govern itself without any interference and should thus be considered to be sovereign.

One might however argue that each of these principles have, to varying degrees, been compromised by the UK's membership of the EU. That Parliament may not make laws in certain areas where competence over a particular subject matter has been assumed by the EU. That this delegation of legislative power to the EU's institutions as enacted by previous parliaments has inextricably bound present and future parliaments. That, in any case, our laws are regularly challenged and struck down by the EU's courts.

But are any of these contentions true and, if so, does this make Parliament any less "sovereign"? 

Parliament may make any law it so wishes

The UK has exercised its sovereign right to enact whatever law it so wishes.

The UK's membership of the EU actually derives from an Act of Parliament (the European Communities Act 1972) under which the UK agreed that in certain areas, primarily those areas required in order to give effect to the Common (now Single) Market, we would permit EU laws to be incorporated (either directly in the case of Regulations or indirectly via implementing Acts of Parliament in the case of Directives) into the UK law.

Laws such as the European Communities Act which effectively delegate legislative responsibility over particular matters to another body are not particularly uncommon. In fact, Parliament regularly delegates its authority to make laws to bodies such as local councils and devolved assemblies such as those in Wales and Northern Ireland. In some cases, a considerable amount of legislative power can be delegated, including in some instances the right to amend the prevailing rate of taxation, as is currently being contemplated in Scotland.

In the case of the EU, the situation is clear.  The European Union Act (2011) states that "Directly applicable or directly effective EU law... falls to be recognised and available in law in the United Kingdom only by virtue of [the European Communities Act]." In effect, EU law is only incorporated into UK law by virtue of the laws passed by a sovereign Parliament permitting it to be so.

In each case, the UK has exercised its sovereign right to enact whatever law it so wishes.

Can an earlier decision of Parliament bind a future Parliament? 

In the past 40 years there has been considerable evolution in the UK's relationship with the EU. There have been treaties executed among Member States which have increased the size and scope of the Single Market, which have created new and augmented existing EU institutions and which have increased the number of Member States. There has been a steady stream of implementing legislation which has implemented new or amended existing EU Directives. In some instances, these implementing acts have "gold plated" the requirements as set out in the relevant Directive, effectively going further or imposing stricter requirements within the UK in a particular area than may actually required by EU law or which may otherwise have been implemented across other Member States.

Again, each parliament has asserted its sovereign right to amend, supplement or remove existing laws in order to give effect to developing EU law for the purposes of fulfilling the UK's consistent and long-standing policy objective of ensuring access to the single market.  In the face of such radical evolution, there is simply no argument to be made that any contemporary Parliament has felt bound by the actions of their predecessors nor that they actually were bound by their predecessors as a matter of constitutional law.

 A valid Act of Parliament cannot be challenged by the Courts

It is often argued that validly enacted laws of Parliament may be challenged and rendered unenforceable by the decisions of the European Court of Justice (the ECJ). However, is this indeed the case? To answer this, we first need to establish what the ECJ actually does. In simple terms, the ECJ has judicial competence over matters pertaining to EU law. This role is important as it creates a forum among all Member States whereby disputes relating to a point of EU law can be resolved such that the Member States may be confident in the consistent interpretation and application of EU law across the single market.  

However, by exercising its sovereignty in enacting a law which facilitates the creation of a court which is, arguably, superior to our own Supreme Court, has Parliament voluntarily relinquished its own sovereignty?

To make such an argument would be to fundamentally misunderstand the purpose and competency of the ECJ. The ECJ works in tandem with national courts, who may refer questions on EU law to the ECJ. The ECJ may not assert jurisdiction over matters without such matter having been first referred to it by the relevant national court of a Member State. The ECJ ruling is limited to matters within its competency i.e. matters relating to the interpretation or application of EU law. 

It does not follow that an ECJ judgement may directly strike down a validly enacted Act of Parliament. Of course, there may be instances when, for example, a previously enacted Directive may be found to have been implemented incorrectly across a number of Member States and it may follow that the corresponding Act of Parliament may need to be revised in order to correctly reflect intended application of the relevant Directive. This is patently not the same as the ECJ randomly or capriciously striking down national laws over which they have been granted no competence by the Member States. 

Finally, it is important to remember that the ECJ is empowered to render such judgements only through the operation of the EU Treaties, each of which having been endorsed and enacted into law through the actions of a sovereign Parliament. 

Is Parliament sovereign?

This is not a question that is often debated outside of law libraries or academic circles. It is a matter of some curiosity that the question of parliamentary sovereignty has assumed such prominence in the current debate on EU membership, certainly when viewed in comparison to the more tangible and emotive arguments surrounding the economy or immigration.  

It is, however, an important question. The sovereignty of Parliament is the key principle upon which the UK's unwritten constitution depends. To assert that Parliament is somehow not sovereign, is to fundamentally undermine the constitution and the entire body of common law upon which our society depends.

In determining whether or not Parliament is sovereign, it is important to distinguish the question from criticism of the EU's institutions or its law-making processes. To argue that the EU is somehow undemocratic, unrepresentative or even dictatorial or that membership of the single market is not worth the level of control currently delegated to the institutions of the EU is largely irrelevant in assessing whether or not Parliament remains sovereign. 

It is undeniably true that the institutions of the EU exercise some control over certain areas of our polity. However, in the same way that the Northern Irish assembly has assumed authority over schools in County Derry or that Essex County Council retains control over the roads of Colchester, this authority is only granted to these institutions by the grace of Parliament and by virtue of legislation read, debated and validly enacted by a sovereign Parliament in pursuit of the policy objectives of the government of the day.

It seems clear therefore that, notwithstanding passage of the European Communities Act and all subsequent Acts of Parliament which have served to broaden and deepen the UK's relationship with the EU, Parliament has never relinquished its sovereignty. The argument that a body which is currently considered sovereign in the strict constitutional sense may, at some point in the future, forever relinquish its sovereignty is inherently paradoxical. Having legislated for the incorporation of EU law into UK law in the past, a future Parliament may "reassume its sovereignty" at any point and may, by the enactment of an Act of Parliament, determine that it will no longer be bound by EU law, engage in deliberations with the ECJ nor concern itself with the operation of the various EU institutions.

Indeed, if this weren't possible, what would be the point in having a referendum on EU membership at all?

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