Supreme court told PM will ‘abide’ by any ruling but minister declines to say if MPs could be sent away again immediately

Boris Johnson has given an undertaking to the supreme court that he will “abide” by any ruling it makes about recalling parliament but a government minister declined to be drawn about whether MPs could be sent away again immediately.

Addressing an emergency hearing of the UK’s highest court, Lord Keen QC, who is a justice minister and one of the two lawyers representing the prime minister, resisted judicial requests for further pledges guaranteeing parliament’s return.

The sometimes testy exchanges between the government’s lawyer and a series of senior supreme court justices came on a day when the political row over Brexit focused on the minutiae of courtroom arguments about Johnson’s advice to the Queen to prorogue parliament for five weeks.

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The hearing opened on Tuesday with anti-Brexit protesters massing outside the supreme court, directly opposite parliament in Westminster, bearing signs declaring: “Don’t silence our MP”, “Reopen parliament” and “They misled the Queen”.

Eleven supreme court justices are sitting for three days to consider appeals from the high court in London and the appeal court in Edinburgh, which reached diametrically opposed views on the lawfulness of Johnson’s actions. The English court ruled it did not have legal authority to examine the prime minister’s decision; the Scottish judges declared he had acted illegally to stifle debate in the Commons.

Before arguments formally opened, Lady Hale, the supreme court president, acknowledged that it had “serious and difficult questions” before it. That was evidenced, she said, “by the fact that three senior judges in Scotland have reached a different conclusion to three senior judges in England and Wales”.

She continued: “The supreme court exists to decide such difficult questions of law and we shall do so in accordance with our judicial oath ...” which declares that the judges will reach their conclusion “without fear or favour, affection or ill will”.

Lawyers for the prime minister said in written submissions that the claimants’ argument risked creating a principle which “would involve the courts entering the political arena”.

In the afternoon, Keen told the court that he was giving “a clear undertaking that the prime minister would respect” the court’s eventual judgment. Kerr, a justice from Northern Ireland, then asked him: “Can we take it that he [Johnson] wouldn’t apply to have parliament prorogued again?” Keen replied: “I’m not in a position to comment on that. That will have to be addressed by the decision maker [ie the prime minister].”

Keen, who is also the advocate general for Scotland, also told the supreme court that parliament could have resisted Boris Johnson’s advice to the Queen to prorogue the session and voted to resist the order to close it down for five weeks.

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His surprising assertion assumed that because parliament had chosen not to act, the courts should not be able to overrule what parliament itself had chosen not to do. If parliament could pass an act preventing a no-deal exit from the EU, Keen said, it could also have legislated, adopting mechanisms within the Northern Ireland Executive Formation Act 2019, to prevent itself being prorogued.

Legal argument reached back as far as the often-cited 1610 Case of Proclamations, which imposed limits on the royal prerogative, and referred to William IV as the last monarch who in the 1830s exercised the royal right to prorogue parliament in person.

There were robust exchanges over the political precedent set by the postwar Labour government’s decision to prorogue parliament twice in 1948. “It was a naked political use of the prerogative to force through its intended legislation notwithstanding it had no consent in the House of Lords,” Keen told the supreme court.

But Lady Hale intervened: “It could be said it was in pursuit of democracy rather than opposed to it. To enforce the will of the House of Commons [to exert its authority over the unelected Lords]...” Keen replied that prorogation on that occasion was an example of a government doing so “where the executive wish to pursue a political objective and they are entitled to do so”.

Earlier Lord Pannick QC, who represents the businesswoman and legal campaigner Gina Miller, alleged that Johnson’s motive for introducing a Commons prorogation of five weeks was “to silence parliament for that period”.

The prime minister’s extended suspension of MPs’ debate was carried out for an “improper purpose”, he added, to “avoid the risk of parliament undermining the policies of his executive”.

“The prime minister’s advice to Her Majesty to prorogue parliament for a period of five weeks is an unlawful abuse of power,” Pannick told the court.

“[His] reasons for advising on a five-week prorogation were improper in that they were infected by factors inconsistent with the concept of parliamentary sovereignty, in particular his belief that parliament does nothing of value at this time of year and his concern that parliament might take steps which would undermine the government’s negotiating position with the EU.”

A Northern Ireland prorogation claim, argued on behalf of Raymond McCord, a victims’ rights campaigner whose son was murdered by loyalist paramilitaries, will be heard on Thursday. Permission has also been given for five other interveners. They are: the lord advocate for the Scottish government, the counsel general for Wales, Sir John Major, Lady Chakrabarti, the shadow attorney general, and the Public Law Project.

The hearing, which is due to last three days, continues. The court, which is sitting for the first time ever outside its normal legal terms, is not expected to deliver to deliver its judgment before the end of Thursday at the earliest.