This final report summarises the key developments in court on Wednesday and Thursday. The transcripts for both days are here and here.

Lord Pannick QC finished his submissions on Wednesday morning, covering the legality of the use of prerogative powers to frustrate legislation, the absence of any Ministerial power to trigger Article 50 in EU-related Acts of Parliament made after 1972 and the need for an Act, rather than any other Parliamentary step, such as a motion in both Houses, to give the authority the law demands.

He began with a guided tour of the 1972 European Communities Act, explaining how section 2 protected the Act against being repealed by implication through later Acts of Parliament, making ministerial action to set it aside very unlikely, and that section 3 would make no sense at all if the Government is right.  He then took the court to the European Parliamentary Elections Act 2002.  If the Government is correct, he said, Article 50 could be invoked nullifying every right it created despite the Act remaining on the statute book.  Similarly, the Communications Act 2003  imposed regulatory functions on Ofcom to enforce EU law which would be senseless were Article 50 invoked without Parliament first deciding how to deal with them. Parliament needed to be fully involved so that its intentions in passing such legislation were not frustrated.

Next, Lord Pannick discussed the De Keyser case. “Have I been mispronouncing that case all my adult life?” asked Lady Hale. “You say De Keyser, I say De Keyser” quipped Lord Pannick, making the first joke in legal history to be reproduced for charity in T-shirt form.

“Whatever it is called” he continued “that is not the only type of case where the courts will impose limits on the exercise of prerogative power. Here, we submit there simply is no prerogative power to act under a treaty so as to defeat, nullify, frustrate statutory rights. That is one additional principle. Another principle is where the exercise of prerogative powers would frustrate the provision made by Parliament; that is ex parte Fire Brigades Union.”

Mr Eadie was therefore wrong, said Lord Pannick, to argue that the De Keyser case set the only limits on prerogative power. As for the argument that post-1972 legislation showed Parliament setting limits on the prerogative but deliberately choosing not to  in relation to Article 50, this was wrong too because the Green Paper for the Constitutional Reform and Governance Act 2010 showed  the Government’s intention had been only to replicate the Ponsonby Rule  and was mindful of further  legal protection where there are “treaties that require changes to UK law… the enactment of prior legislation which, of course, requires the full assent of Parliament”. Other statutory changes had been made to increase the powers of the then European assembly.

Lord Pannick and the Justices then debated the effect of the 2015 EU Referendum Act.  Might it be said that the 1972 Act had ‘clamped’ the Government’s power to use the prerogative to change law but the 2015 Act had “dismantled” that clamp, asked Lord Kerr. Lord Pannick said that must be wrong because the 2015 Act said nothing at all about empowering ministers, less still changing 40 years of constitutional arrangements, and would need very clear language to have that effect. What legal effect did it have then, Lord Neuberger wondered. Lady Hale beat Lord Pannick to the answer: “But the Act did have an effect.  It provided for the referendum.”

Last, Lord Pannick discussed what would need to happen were the court to dismiss the appeal – nothing short of express parliamentary authorisation for the invocation of article 50 would do and that would need to be in the form of an Act, not a resolution because only an Act can change the law.  Lord Sumption summarised this point neatly a little later: “resolutions are political acts, whereas legislation directly affects the law.” 

Dominic Chambers QC followed with submission for Mr Dos Santos, tracing the history of the parliamentary sovereignty principle, the way it dovetailed with EU law (“EU law rights solely take effect under English domestic law through the will of Parliament”) and the 2015 Act. It was identical in structure and purpose to the Act which set up the 1975 EEC referendum, that time, the Government had accepted Parliament would need to pass further legislation had there been a ‘leave’ majority.

Next  the court heard from QCs David Scoffield and Conan Lavery arguing the appeals brought against Mr Justice McGuire’s judgment in the McCord, Agnew and others case which  was decided a few days before  the Divisional Court gave judgement and came to a different conclusion. Mr Scoffield first argued that the Northern Ireland Act 1998, like the 1972 Act, was not neutral on the U.K.’s continued membership of the UK – it assumed that it would be a member and created rights and duties based on the assumption with the effect that it would need to be repealed, or substantially amended, before notice could be given under Article 50.  It was a “further conduit” for EU law to pass into UK law. Both the Good Friday Agreement and the British-Irish Agreement reinforced this, he said, as was recognised by Lord Bingham in the Robinson case.

Secondly, invocation of Article 50 without Parliamentary authority would “circumvent” the arrangements had been made with Northern Ireland for legislative consent motions endorsing future constitutional changes. In other words, the Government was attempting to use a prerogative shortcut when the lawful route involved consultation with the representatives of the people of Northern Ireland. Mr Lavery said he went even further. “It would be unconstitutional to withdraw from the EU without the consent of the people of Northern Ireland”, he submitted, because “being part of the EU was “part of a constitutional settlement” envisaged by the Good Friday agreement and there had been “a partial transfer of sovereignty”.

They were followed by the Lord Advocate of Scotland, James Wolffe QC, who argued “the power to change the laws of Scotland were given to parliament, and to those who parliament has authorised, and not to the Crown”. That sounded in the Claim of Right Act 1689 and the Act of Union of 1707. The Sewel Convention meant “that Westminster would not normally legislate with regard to devolved matters in Scotland without the consent of the Scottish Parliament”. When it came to invocation of Article 50 “the United Kingdom has to make that decision in accordance with its constitutional requirements. I say that those constitutional requirements include an act of parliament” and that Act had to be preceded by a legislative consent motion in the Scottish Parliament. 

Mr Wolffe’s submissions were concluded on Thursday morning. He was followed by Richard Gordon QC for the Welsh Government who made an opening submission that the case was “elementary, a child of six, with respect, could understand this point”. Lord Carnwath was sceptical “your child analogy does not really work, because obviously the child is told he cannot go out in the garden, still has the power to go out in the garden, and indeed he may well disobey the constraint and do it.”

Mr Gordon then developed similar arguments to those of the Scottish Government. Consultation with the devolved administrations over certain decisions was “the only glue” holding together the UK constitution. By evading the, the Government was trying to “drive through” constitutional change of a “seismic nature”. But some Justices wondered what this added to the main Miller argument. Lord Mance asked “If we agree with Lord Pannick and reject Mr Eadie, your case is largely unnecessary, except insofar as you rely on the Sewel convention.” Mr Gordon replied “Yes. Yes.”

Next was People’s Challenge QC, Helen Mountfield, the first and only female advocate to speak in the case (though not the only barrister – Anneli Howard and Jess Simor QC are in the Miller and Dos Santos teams).

“My clients are a group of ordinary British citizens, and a Gibraltarian citizen.” Helen began.  “They are all people who will be affected, in very significant aspects of their lives, by a decision to leave the EU and the profound changes that this decision will make to the law of the United Kingdom and their rights as European citizens. They have been crowd-funded by many thousands of relatively small donations from private individuals.”

They were not asking the Court “to decide whether, in the light of the result of the referendum, the United Kingdom should leave or should not leave the EU.   Nor is it being asked to compel either the government, or Parliament, to do anything. All the Court is being asked to do is to consider whether, as a matter of law, an intended act of the Appellant, to notify the EU of a decision to leave on behalf of the UK, would be lawful in the absence of express statutory authority.”

By arguing that authority was not needed Mr Eadie “invites this court to find that ‘the Government can  trigger Article 50 in exercise of the royal prerogative, even though this will alter domestic law, because it has what he described as “untrammelled” or “unconstrained” prerogative power. We disagree. We reject the false assumption that the foreign relations prerogative extends to permit the government to dispense with national law.” 

Mr Eadie had chosen the wrong starting point for the legal analysis “because it conveniently by-passes the biggest hurdle which he faces in his appeal.” The right one was to ask “what are the limits if any of the prerogative power to make and unmake treaties?” 

The answer to that was that “there is no prerogative power to change or dispense with the law as it stands outside the prerogative, whether that pre-existing law is contained in the common law or in Acts of Parliament”. That was clear from the ‘historical inquiry’ Lord Bingham had said was needed in all case where prerogative power was in dispute. Mr Eadie had accepted that, Helen added, “but it is striking that despite positively commending that approach to you, Mr Eadie did not undertake any such enquiry, but put his claim for a wide untrammelled prerogative to change the law at the basis of general assertion.” 

The People’s Challenge team had undertaken the inquiry, she said, and the results were striking, Helen explained. The Case of Proclamations, the Bill of Rights, Article XVIII of the Union with Scotland Act 1706, the King v London County Council, Bancoult No 2., Nicklinson, Pretty, Fitzgerald v Muldoon, Fire Brigades Union and Hayden all show that the prerogative cannot generally be used to dispense with or suspend the law of the land. And there was nothing special about the foreign relations/treating making prerogative in this sense as the authorities in our Written Case demonstrated. There was an “orthodox” answer to the question the case raised. The historical cases gave the answer: the foreign relations prerogative cannot be used to change the law or to vary the sources of law which apply in the UK.

Further, though no judge had been asked to decide whether the UK could withdraw without an Act of Parliament, a series of them had said they assumed that was so. For example, in Blackburn Lord Denning had said “[i]f her Majesty’s Ministers sign this treaty and Parliament enacts provisions to implement it, I do not envisage that Parliament would afterwards go back on it and try to withdraw from it. But, if Parliament should do so, then I say we will consider that event when it happens. We will then say whether Parliament can lawfully do it or not.”

Helen’s second key submission was that, by triggering Article 50, the Government would in fact dispense with law, and remove EU law rights. The People’s Challenge group and those who support them “consider that their EU citizenship is a fundamental part of their identities and that, if they are to be deprived of it, their elected representatives in Parliament should, in law, be responsible for that”, she told the Court.

EU law, and the rights that flowed from citizenship “is part of domestic law so far as this court is concerned, ‘because Parliament has so willed’” as Lord Mance had said in the Pham case.

Yet the Government argued that by passing the 1972 Act “Parliament simply created an empty legal vessel, which the Minister could, at any time, fill or empty at will by using his foreign relations prerogative.” That, Helen submitted, “is not right on the language of the Act, and it is not right when you look at statutory intention.” It could not be squared with the EU Treaties themselves becoming a feature and source of law under the 1972 Act, its purpose or the very serious consequences for rights that could not be replicated if the Government was correct.

Helen finished her submission by responding to two questions the Justices had raised earlier in the week. First, could the 2015 EU Referendum Act in some way revive or legitimize use of a prerogative power put into abeyance by the 1972 Act? The answer was ‘no’. There was no power to do away with rights in the first place, but even if that was wrong, clear, and express statutory language was needed. The 1972 Act was a constitutional statute. It could not be overridden by assumptions or implications. To hold that the 2015 Act, by implication had such an effect would be an act of judicial legislation. As for the legislative arrangements for making a decision on whether another state could withdraw from the EU, these had nothing to do with the UK’s own withdrawal.

The People’s Challenge was seeking “to uphold the Divisional Court’s judgment not only for its determination of the issue before this court, but also because of the importance, in a democratic society, based on separation of powers and the rule of law”. The Court should dismiss the Government’s appeal.

There was an immediate and positive reaction to Helen’s submissions on social media and later from press commentators such as the Guardian’s John Crace.

Helen was followed by Manjit Gill QC speaking for non-EU national carers of EU national children. “This is no time to turn a flexible constitution into a slippery one and let go of its bedrock fundamentals”, he argued. Patrick Green QC for Fair Deal for Expats then argued that ministerial involvement in EU law making was illustrative of parliamentary sovereignty in action, not unrestrained use of the prerogative.

Lord Keen QC and James Eadie QC then mounted their last stand for the Government on devolution issues and the main issues in the case respectively. “We do not assert a power to repeal the Dangerous Dogs Act,” Mr Eadie began, taking the Court back to one of Lord Pannick’s first submissions about that legislation having greater constitutional status than EU law if the Government was right. But it backfired. Had the Dangerous Dogs Act being an EU directive, but identical, it could be disapplied using Article 50, he accepted. Mr Eadie’s closing gambit was to draw attention to Wednesday’s House of Commons resolution calling on the Government to give notification. This too failed to impress the Justices. “If the resolution had been enough for your purposes, then there would have been no need for this appeal” Lord Sumption shot back.

Lord Neuberger adjourned the case indicating that judgement would be forthcoming in the New Year as soon as possible.

Before then, there will be one further update discussing what could happen next, depending on the outcome.