Johnson prorogued parliament for five weeks at the beginning of September. However, the court said that Johnson’s advice to the Queen, which prompted the suspension of parliament, was unlawful because it had the effect of “frustrating or preventing the ability of parliament to carry out its constitutional functions without reasonable justification.”
In her ruling on Tuesday, Baroness Hale, president of the Supreme Court, said that "the effect on the fundamentals of democracy was extreme."
So what happens next?
More time to avoid a no-deal Brexit
It means parliament can be recalled immediately, which gives MPs extra time to prevent a no-deal Brexit.
Joe Armitage, a parliamentary procedure adviser at Global Counsel, believes that MPs might use the extra parliamentary time to push for additional legislation forcing Johnson's hand in the negotiations with the EU. Or, he said, they may try and initiate contempt proceedings against the government over its selective – rather than full – release of information demanded by MPs a fortnight ago.
“MPs could potentially use the extra parliamentary time in the lead up to the European Council meeting on 17-18 October to influence the government’s Brexit negotiating strategy, perhaps by passing additional legislation,” he told Yahoo Finance UK.
“They might also initiate contempt proceedings against the government for failing to publish the private communications between government advisers relating to prorogation.”
However, Dom Walsh, a policy analyst at the influential Open Europe think tank, doubts that the MPs will use the time regained effectively.
“Prorogation meant parliament lost up to five weeks of debate; assuming it is recalled, this has now been cut to two weeks,” he told Yahoo Finance UK.
“So while this is an important moment, it is not clear what parliament will be able to do in three extra weeks that it had not previously done over a period of many months. And with the Benn Bill already in law, they have already succeeded in tying the prime minister’s hands.”
The Benn Bill is the legislation presented by Labour MP Hilary Benn, and signed by opposition leaders and Conservatives recently sacked by Boris Johnson, including Alistair Burt and Philip Hammond. It requires the government to either reach a deal – or gain parliament's approval for a no-deal Brexit by 19 October.
“With regards to the next developments of Brexit, the question is not just whether parliament is sitting but what it is prepared to do,” Walsh said.
Article 50 extension
Andy Silvester, the deputy editor of City AM made a similar point on Twitter – MPs have voted against May’s first and second deal, European Free Trade Association/European Economic Area both with and without the single market, the Customs Union with and without single market alignment, a Withdrawal Agreement without the political declaration, and a no-deal Brexit too.
The only item which has consistently been able to pass in terms of Brexit is an extension to Article 50, which achieves nothing other than kicking the can down the road. And with the Benn bill already passed, it is unclear how the retention of a few weeks of parliamentary debate will solve a crisis which has not seen, let alone a conclusion but anything close to it, since the Brexit process began.
With John Bercow indicating parliament will be recalled for 11.30am on Wednesday, Armitage believes problems will be caused for the government.
“I think both Johnson and Raab are currently abroad so maybe they won't be able to do PMQs, or if either of them do then they might be jet-lagged. It's unlikely that MPs will vote for the periodic adjournment motion to allow the Conservative party conference to take place next week.
In response, the government could, in theory, ask the Queen to prorogue parliament again but this time for a shorter period of, perhaps up to Thursday next week. That would be ... rather incendiary, though,” Armitage said.
No matter what happens, the next three weeks are unlikely to be quiet. When asked about what they thought of the “incendiary” strategy, one shadow minister replied: “Good luck with that.”
Despite being a bit of a sideshow with the current Brexit debacle, the shadow minister highlighted that the opposition could cause trouble by highlighting the government’s block of the domestic violence bill, which will be revived by the prorogation being ruled unlawful.