Brexit: What next in the Article 50 judicial review?

The English High Court today held that the UK Government cannot trigger Article 50 of the EU Treaty to commence the UK’s exit from the European Union, or ‘Brexit’, without referring the matter to Parliament. This differs from the earlier decision by the Northern Ireland High Court, where the argument that exit required an Act of Parliament or some other form of Parliamentary mandate was rejected.

Key points in the judgment 

The UK Government had argued that in enacting the European Communities Act 1972 – the legislation which governed the UK’s entry to the European Union in 1973 – the Crown retained its prerogative power to effect a withdrawal from the EU treaties, and thereby the Crown should have the power to choose whether EU law should continue to have effect in the domestic law of the UK or not.

The court rejected this argument, finding nothing in the text of the 1972 Act to support this conclusion.

What happens next? 

The court gave permission to the UK Government to appeal directly to the Supreme Court, bypassing the Court of Appeal. This is known as “leapfrogging”. Leapfrog appeals are only available in exceptional circumstances and usually require the granting of a leapfrog certificate by the trial judge and the grant of permission to appeal by the UK’s highest court, the Supreme Court. In this case, a leapfrog appeal has already been agreed. This is unusual but unsurprising: The case gives rise to significant issues of public law that have rarely if ever been considered in such an important context.

We understand that dates have been set aside in December for the Supreme Court to hear the appeal, most likely before a full bench of eleven judges. Supreme Court hearings are streamed live and this case will garner significant attention, both nationally and internationally.

What is the mechanism for withdrawing from the EU?

Article 50 of the Treaty on European Union provides the legal basis for a Member State to leave the EU. Article 50(1) states that any Member State may decide to withdraw from the EU in accordance with its own “constitutional requirements”. This term is not defined. The question of what the UK’s constitutional requirements are for these purposes has been a key issue in the judicial review proceedings. Under Article 50(2), a Member State that decides to withdraw must notify the European Council of its intention. Once a Member State has given notice, a two year period begins in which a withdrawal agreement is to be negotiated. The Member State ceases to be a member of the EU from the date of entry into force of the withdrawal agreement or, failing that, two years after the Article 50 notification (unless all Member States agree to extend).

For more information see: Brexit: What happens next?

What difference does an Act of Parliament make?

If an Act of Parliament is required before the Government can trigger the UK’s exit from the EU, the standard procedure for creating a new law will presumably have to be followed.

The process begins with the drafting of a Bill. This is followed by a number of readings of the Bill in the House of Commons, along with detailed examination of the Bill by committee and a reporting stage. There is the opportunity for debate at various points along the way. After the final reading, Members of Parliament vote on whether the Bill should be approved. The Bill follows a similar process through the House of Lords. Final amendments are then considered. Once passed, a Bill needs to receive Royal Assent before it becomes an Act of Parliament.

The effect of this process is that there will be the opportunity for another airing of the arguments for and against leaving the EU in both the House of Commons and the House of Lords. There is also likely to be debate about how the exit negotiations should be conducted, and the form of any withdrawal agreement.

The outcome of the vote on the Bill is unpredictable. Most MPs are thought to have voted for the UK to stay in the EU. We are not aware of any analysis of the views of members of the House of Lords, but the Constitution Committee of the House of Lords published a report in September 2016 which concluded that it was constitutionally appropriate for the assent of Parliament to be sought for the triggering of Article 50. This, they said, could be achieved either by an Act of Parliament or a resolution stating Parliament’s approval for the triggering of Article 50. Clearly therefore the House of Lords sees Parliament as having an important role to play in the Article 50 process. All that said, it would be difficult for Parliament to ignore public opinion on Brexit, as evidenced by the outcome of the referendum.

In October 2016, Theresa May announced that she would trigger Article 50 by the end of March 2017. This timing could now be at risk.

What else do you need to know?  

The court was not asked to decide the important question of whether or not an Article 50 notice can be revoked. Indeed the Attorney-General appeared to concede that such a notice, once given, would not be revocable. The Attorney-General’s statement might not be categorical, and there are certainly differing views on this issue. Donald Tusk, President of the European Council, recently suggested that an Article 50 notice could be withdrawn. Others in Brussels disagree. Ultimately this is a question of EU law (with the Court of Justice of the European Union as the final court of reference) rather than of English law.
In Northern Ireland, a similar legal challenge was brought to decide whether the consent of the Northern Irish Assembly is required to trigger Article 50. This challenge was rejected by the Northern Ireland High Court and this case is also likely to be appealed to the UK Supreme Court.


It is fairly unusual for the courts to be called on to intervene in the core workings of the UK’s constitution. For constitutional lawyers, this case represents a rare opportunity to explore sometimes complex legal arguments about the intertwined roles of Government and Parliament. For the rest of us, the outcome is the most important thing. For now, the only clear consequence of the High Court judgment is that Brexit uncertainty is set to continue.

By Hazel Moffat, Camilla MacPherson and James MacGachie