Implications and context of the UK High Court's judgment

The decision

On 23 June, in an advisory referendum called by its government, Britain voted to leave the European Union by a margin of 52 per cent to 48 per cent. One of the few fixed points in the ensuing political and economic uncertainty is that the formal process of withdrawal begins with a notice given under Article 50 of the Treaty on European Union.

Theresa May's government has so far proceeded on the basis that she can give the Article 50 notice at a time of her own choosing (which she has said will be before the end of March 2017) and without reference to Parliament, by relying on Crown prerogative (executive powers). At 10.00 London time this morning, the UK High Court ruled that UK ministers have no power to trigger Article 50 unless and until Parliament confers such power on them1.

With the government confirming that it will lodge an appeal, the action will now move to the Supreme Court, where, as a sign of the seriousness of the issues in question, and the potentially far-reaching political and constitutional effects, the appeal is likely to be heard by all 11 Justices, who are expected to sit in a session currently anticipated to be set down for 7-8 December.

Why was the referendum vote not enough?

Article 50 of the Treaty on European Union states: 'Any Member State may decide to withdraw in accordance with its own constitutional requirements.' The member state must then notify its intention to the European Council and ceases to be a member state two years after giving that notice, unless all the member states agree to allow it a longer period of time to negotiate its exit (and continuing relationship with the rest of the EU).

The Crown prerogative is a bundle of government powers which are not conferred on ministers by statue, but which UK common law recognises as being able to have legal effects in certain circumstances. One important prerogative power is the ability to enter into international treaties, such as those that underpin the EU. The government's case was that it was a matter for ministers, implementing the will of the people as expressed in referendum, to decide when and how to trigger Article 50. Those bringing the case against the government argued that this would mean that ministers would be taking action that would remove important legal rights conferred by Parliament on UK citizens and businesses when it passed the European Communities Act 1972 (ECA) to give effect to the EU treaties that the government of the day (exercising the prerogative) had agreed to sign. Ministers could only have such powers if granted them in statute: no statute, either expressly or by necessary implication, grants them such powers.

In court, Lord Pannick QC, the barrister representing Gina Miller, the lead challenger in the claim, said that triggering Article 50 was like "pulling the trigger and once pulled the bullet hits the target". It inevitably leads to the consequence that the ECA ceases to apply. “This is not simply action on the international plane [where the claimants accept that ministers can rely on the prerogative]… It leads to the removal of a whole series of important rights whatever Parliament may think about it later.” The court concluded firmly in favour of the claimants, finding that the arguments made by the government were "flawed" at a "basic level", because they gave "no value to the usual constitutional principle that, unless Parliament legislates to the contrary, the Crown should not have power to vary the law of the land by the exercise of its prerogative powers".

Both sides agreed that, for the purposes of the case, any Article 50 notification should be treated as irrevocable, thus Lord Pannick's rhetorical flourish about pulling the trigger, with the point being that any notification would be irretrievable2. This is a separate point from the government's concession that it would be "very likely" MPs would be able to vote on the final Brexit agreement reached between the UK and the European Union – at that stage it will simply be too late to revoke the notification, meaning that, once it is started, the UK will be outside of the EU at the end of the two-year period, regardless of what, if any, deal is then presented to Parliament for approval.

Consequences of the current decision

Thus, the determination of when and how the UK pulls the trigger on its departure is a critical one to settle before the government can even start to negotiate any terms of departure and enact domestic legislation to implement Brexit. This of course is before it can begin to start the process of securing the long list of international trade agreements and arrangements in many different areas to replace those from which it currently benefits as an EU member.

Public opinion certainly seems to back some form of parliamentary scrutiny of the Brexit negotiations, with a poll commissioned by the Open Britain campaign3, showing that nearly three-quarters of the public thinks the government should seek parliamentary approval for its Brexit plans before Article 50 is triggered and the negotiations start. Interestingly, Leave voters amongst those polled backed the move by 49 per cent to 33 per cent and UKIP voters were the most enthusiastic, backing the move by 62 per cent to 20 per cent.

How much does all this legal debate over the constitutional details matter? From one point of view, it may all be something of a distraction from the core issues in the UK's Brexit debate, like the terms of the UK's exit from the EU and its future trading relationships. However, if the Supreme Court reaches the same conclusions as the High Court, and if – as Lord Pannick has argued – the only way for Parliament to authorise ministers to trigger Article 50 is through legislation, the government will not be able simply to propose a parliamentary motion to issue notice or not, thereby challenging MPs and Peers to vote against the "will of the British people" or approve the government's planned March 2017 deadline. Indeed, David Davis, the Brexit Secretary, confirmed as much in an interview with Sky News this afternoon, saying that, if the government's appeal to the Supreme Court fails, it will have to pass an Act of Parliament to effect the Article 50 notification. Asked if it would be possible for the government simply to allow MPs a vote on a narrow resolution, his response was 'That’s not available'.

Instead, ministers will have to prepare a Bill to give them the necessary authority and, once a Bill is in play, members of both Houses of Parliament are likely to want to introduce amendments to it that go beyond simple authorisation to give an Article 50 notice. As a result, the government may be forced to concede to Parliament a greater role in the exit process than it has been willing to do so far. In the meantime, the economy continues to send out mixed messages about its strength and performance post-vote, with the Bank of England now revising its output growth forecasts up in the near term but down in the longer term, with its central projection being that inflation rises from its current level of 1 per cent to around 2¾per cent in 2018, before falling back gradually over 2019 to reach 2½ per cent in three years' time4. "Events" – and political reactions to them – are likely to have as much of an effect as constitutional argument as we continue to seek clarity in an uncertain era.