In a landmark constitutional law ruling (R(Miller) v Secretary of State for Exiting the EU) the High Court today held that the UK Government cannot trigger Article 50 of the Treaty on the European Union (Article 50) without the approval of Parliament. It was common ground between the parties that notice under

Article 50(2), which starts the formal process for the UK leaving the EU, is not reversible. Accordingly, serving notice would inevitably lead to the loss of legal rights arising from the UK's membership of the EU which have been enshrined in domestic law. However, as Parliament had legislated to confer these rights in domestic law, only Parliament could take them away: the executive branch of Government could not rely on its prerogative powers to make and break treaties to do so.

The ruling is a victory for the claimants who brought the case against the Government's position that it would trigger Article 50 through the use of the Royal Prerogative. The Government has announced that it will appeal today's ruling and the Court has made arrangements for a leapfrog appeal to be heard by the Supreme Court (hearing dates have been scheduled on 7 and 8 December 2016 with a full court in sitting in view of the constitutional importance of the issue), in order to ensure a final position on this issue before the Government's March 2017 timetable for triggering Article 50.

However, this timetable may not be feasible if the Supreme Court upholds the High Court's decision. Although the judgment does not expressly state the form of parliamentary approval required for the Government to be able to issue a notice under Article 50, the logical implication of the Court's decision is that primary legislation would be required, and there is the potential for any such legislation to become mired in the Parliamentary process.  

1. Background to the case  

Article 50 sets out the procedure for the withdrawal of a Member State from the EU. Article 50(1) requires the withdrawal of a Member State to "be in accordance with its own constitutional requirements". Once triggered, a two year timeline starts to run at the end of which the relevant Member State must leave the EU, regardless of whether a formal withdrawal arrangement has been agreed. The other Member States may decide, on a unanimous vote, to extend this period.

As a general rule, in the UK, the conduct of foreign affairs, including the making and unmaking of treaties, involves the exercise of prerogative powers – a residue of powers exercisable by the Crown acting through the executive branch of Government. The Government therefore claimed that it could trigger Article 50 through the use of the prerogative, without involving Parliament. By issuing a notice under Article 50, it will simply be giving effect to the will of the people expressed in the June referendum under the Referendum Act 2015. Parliament would, in any case, have an opportunity to vote on any withdrawal treaty negotiated with the EU.

This approach was challenged before the High Court. The claimants argued that triggering Article 50 without prior authorisation of an Act of Parliament is not in accordance with the constitutional requirements of the UK, because "it would frustrate the rights and duties enacted by Parliament in the European Communities Act 1972, and would be inconsistent with the object and purpose of that Act, namely to give effect to the rights and duties consequent on membership of the EU". Any opportunity for Parliament to vote on the terms of an exit treaty once negotiated with the EU is too late, because triggering Article 50 will start an irreversible process of withdrawal.

2. The judgment

The Court made it clear that the case was not concerned with the merits of leaving the EU, a political issue, but instead related to a point of UK constitutional law - whether the Government is entitled to give notice of the UK's decision to leave the EU under Article 50 by exercising the Crown's prerogative powers without reference to Parliament.

At the heart of the challenge was a potential conflict between different constitutional principles. The Government's case focused on the executive's prerogative power to make and break treaties, and claimed that nothing in the legislation enacting EU law domestically (primarily the European Communities Act 1972 (ECA)) abrogated or limited the scope of this prerogative power, which was sufficient to give notice under article 50. However, the claimants (and ultimately the Court) focused on a higher constitutional principle: the supremacy of Parliament in the UK's constitutional order. Whatever their scope, the executive could not rely on prerogative powers to override rights conferred through legislation enacted by Parliament.

It was accepted that giving notice under Article 50 would inevitably have the effect of changing domestic law. The Court considered three categories of rights arising under EU law: (i) those capable of being replicated in domestic law once the UK left the EU (eg workers' rights under the Working Time Directive); (ii) those enjoyed by UK nationals in other EU states; and (iii) those that could not be replicated in domestic law once the UK left the EU (eg the right to vote in elections to the European Parliament). These rights would eventually be lost through the triggering of Article 50, even if some could be replicated though new legislation.

According to the Government, when Parliament enacted the ECA, it must have intended that the Crown would retain its prerogative power to withdraw from the EU, and that the Crown should also have the power to choose whether or not EU law should continue to have effect under UK domestic law. The Court dismissed this argument on the basis that there is nothing in the ECA to support it. As a matter of constitutional law, the Crown has no power to change domestic law and nullify rights under the law unless Parliament confers on the Crown authority to do so. Parliament cannot have intended to leave the continued existence of all the rights introduced into domestic legislation by virtue of the ECA subject to the choice of the Crown in the exercise of its prerogative powers – especially given the ECA's fundamental importance to the constitutional structure of the UK. It is for Parliament, not for the executive, to repeal legislation.

The Court agreed with the claimants that ratification by Parliament of a withdrawal agreement negotiated by Government would do little to safeguard these rights. Should Parliament refuse to ratify any such agreement the effect would simply be a withdrawal without any safeguards at all for any of these rights.

On the argument that the Government is simply giving effect to the will of the people expressed in the June referendum, the Court makes it clear that under UK constitutional law a referendum can only be advisory unless very clear language to the contrary is used in the referendum legislation in question. This was not the case for the Referendum Act 2015, which was passed on the basis that it would have advisory effect only. Parliament must have appreciated that this had to be the case, as a vote to leave would inevitably leave for future decision many important questions relating to the legal implementation of withdrawal from the EU.

Although this judgment and the judgment of the High Court in Belfast in the McCord case dealt with different issues and the Courts sought to avoid any overlap, there is one issue on which there appears to be an inconsistency between the decisions. In McCord, the Court found that notification under Article 50 would only "probably" lead to changes in the law of the UK, whereas in this case the parties had accepted that it would inevitably have such an effect. Our note on the McCord case can be found here.

3. Comment  

Given the pending appeal, it is too early to say how this case will shape the Government's approach to Brexit. If the Supreme Court upholds the decision, however, it is difficult to see how the Government will be able to continue the approach it has taken to the negotiations so far unless Parliament quickly confers a power to trigger Article 50 without adding substantive qualifications, limitations, or additional requirements.

The case also proceeded on the agreed basis that giving notice under Article 50(2) was irreversible. This strengthened the claimants' argument that giving notice would inevitably lead to the loss of rights currently underpinned by statute. The irreversibility of an Article 50(2) notice has been subject to debate, and if the Supreme Court was not prepared to proceed on that basis then there is at least the theoretical possibility that a reference to the Court of Justice of the European Union would be required to settle the point, which would surely prove controversial and introduce more delay into the process. The Government has made it clear that it will not seek such a reference.