The Brexit Legal Challenge- A Summary

Haozhou (Nick) Qiu, J.D. Candidate 2018, Columbia Law School


December 8, 2016 marked the final day of the UK Supreme Court’s hearing on Brexit and Article 50.  Presided over by an unprecedented 11 judges, the case concerned the appeal by the UK government against the November High Court ruling on the matter. The prior judgment stated that notification of an intention to leave the EU under Article 50 cannot be given based on royal prerogative alone; instead, formal legislation by Parliament is required. The Supreme Court hearing lasted four days and the court is expected to deliver its opinion sometime in January.

Background to the legal challenge

The High Court case was brought by Gina Miller, a fund manager in the City of London, and Dier Dos Santos, a hairdresser working in London. The claimants’ primary contention is that Article 50, the treaty provision by which a Member State may leave the EU, cannot be triggered by prerogative power alone. Both the claimants and the court have been keen to stress that the case is not about blocking Brexit or the merits of EU membership. Instead, it is argued to address the correct constitutional procedure by which notice of intent to leave the EU should be given. Despite reassurances from those involved in the case and the academic and legal communities that the process by which the UK will leave is a question of law, the claimants, their lawyers and even the judges have come under personal attack by those who see the entire legal challenge as a betrayal of democracy.

Summary of the High Court Decision

The original challenge in the High Court was heard by three of the most senior members of the judiciary, including the Lord Chief Justice and the Master of the Rolls. The Lord Chief Justice, Lord Thomas, stressed very early on in the judgment that “the court is not concerned with and does not express any views about the merits of leaving the European Union: that is a political issue.”

The government’s key argument was that it is constitutionally proper for the government to give effect to the referendum result and to invoke Article 50. This position was based on the idea that had Parliament wanted to prevent the government from invoking Article 50 if the people voted that way, it would have explicitly said so in the 2015 European Union Referendum Act. In the absence of any restrictions imposed by Parliament, the court should not imply such limitations. It is well settled that the government may exercise prerogative powers to enter into or withdraw from treaties, and invoking Article 50 falls under this domain. Therefore, no legislation is necessary. The government further tried to argue that the claim itself was not justiciable in the courts; the court should not hear a claim that aims to prevent the decision to invoke Article 50 from being made. This argument was promptly rejected by the court as the case was found to be not about the merits but about procedure.

The claimant’s principal argument was that primary legislation passed by Parliament is necessary in order to invoke Article 50. In making their case, claimants relied on the established principle of parliamentary sovereignty: 1972 European Communities Act conferred a substantial number of rights on individuals and the government does not have the power to take away those rights without explicit statutory authority. The government’s response was that the 1972 Act does not, in fact, create any such rights. Instead, the government argued that the Act serves as a mere mechanism that allows rights under EU law to be exercised in the UK and its purpose was not to confer rights onto individuals, but to ensure that the UK properly discharges its obligations as a Member State. (See Mark Elliot). As a result, triggering Article 50 will not remove any rights created by the 1972 Act and no primary legislation by Parliament will therefore be required. This argument is unconvincing. Regardless of whether the primary purpose of the Act was to confer rights or whether the Act was merely a mechanism that ‘transposed’ such rights arising under EU law, the effect of the Act was to allow individuals to enjoy rights that they would not have otherwise enjoyed. Consequently, in order to take away those rights, an Act of Parliament would appear to be necessary.

The High Court ruled that Article 50 could not be triggered by invoking the government’s prerogative power. The court primarily relied on the idea of parliamentary sovereignty and noted that prerogative power cannot be used to alter domestic law or take away rights under the law unless Parliament had expressly or implicitly granted authority to do so. The court found no such authority to exist under the 1972 Act. Consequently, it follows that the government is not empowered to give notice under Article 50. The fact that the electorate had shown an opinion contrary to the 1972 Act does not render that Act invalid.

In addition, the court emphasized the advisory nature of the referendum and the fact that, in a parliamentary democracy, any referendum result will not be binding unless there was express language to that effect in the referendum legislation. Given that there was no such explicit language in the 2015 Referendum Act, from a purely legal perspective, Parliament would be entirely free to vote against triggering Article 50.

Supreme Court Hearing and Devolution

The government made similar submissions to the Supreme Court. A crucial difference between the High Court hearing and the Supreme Court appeal is that the Scottish and Welsh governments were given permission to intervene in the case. Both the Scottish and Welsh governments concurringly argued that the UK government cannot trigger Article 50 based on prerogative power. Further to issues relating to prerogative power, the court also heard arguments addressing devolution and federalism. The Sewel Convention recognizes that the UK Parliament, although it has the power to do so, will not normally legislate on matters affecting Scotland and Wales without prior consent of those areas. This is a particularly contentious issue since Scotland had voted overwhelmingly to remain in the EU and both sides could argue that they represent the will of their people.

May the UK withdraw its notification and could the case end up before the CJEU?

The question of whether notification under Article 50 may be revoked is of paramount political and legal importance. If it is not revocable, then once Article 50 is triggered, there is no going back; UK membership will be terminated within the two-year timeframe set out by Article 50. If it is revocable, however, then there is a possibility that the withdrawal process may be halted if a favorable outcome for the UK was unlikely. Article 50 does not provide a clear answer to this question and the opinions of scholars differ. Both the government and the claimants agree on the fact that notice cannot be revoked. In their submissions, the claimants argued that there is no express provision in Article 50 that allows withdrawal. However, many academics have found this argument to be unconvincing.

Jean-Claude Piris, the director-general of the Council of the European Union’s Legal Service, argues that notification is revocable because it is merely an expression of intent to leave. The notifying country remains a Member State until the two-year period expires. Therefore, should a significant political event such as a general election or another referendum occur, the notifying country may withdraw its notification or change its “intention” and continue to remain as a full Member of the EU. There is nothing in the wording of Article 50 that prohibits a country from unilaterally withdrawing notification. Indeed, it would seem contradictory to principles of democracy and the EU’s best interest as well as that of the Member State concerned to force an exit after a political change of mind had occurred. Lord Kerr, speaking to the BBC, recognized the tension between the legal framework and political realities. Whilst revoking the notification seems to be legally possible, such an act would raise serious political issues. If notification can indeed be revoked, people who voted to leave may justifiably feel frustrated by the number of hurdles they must jump through in order for the UK to terminate EU membership.

Ultimately, whether an Article 50 notification may be revoked turns on a question of EU law and would have to be resolved by the CJEU. Article 267 permits a national court to make a preliminary reference to the CJEU on an issue of EU law. However, such reference is to be made only if a ruling on the question of EU law is, in fact, necessary to decide the case at hand. While there is no doubt that the resolution of this issue is important to the UK in future negotiations with the EU, it is unclear whether it is a necessary question to resolve the case at hand.


The UK government’s plan to invoke Article 50 before March 2017 has no doubt been dealt a rather serious blow by the High Court’s ruling of first instance. While the government has appealed to the Supreme Court, it is unlikely that the Supreme Court will come to a fundamentally different conclusion, since the legal arguments have not changed significantly on appeal. Should the Supreme Court decide to affirm the High Court’s decision, Parliament would have to pass primary legislation before Article 50 could be invoked. This would no doubt create considerable uncertainty regarding the timing of Brexit and whether it would take place at all. The issue of whether notification under Article 50 may be withdrawn is still unclear at this time and it is unlikely to be answered by the CJEU anytime soon. However, it may become a deciding factor later in the Brexit process if Article 50 is eventually invoked.