Boris Johnson's decision to suspend parliament is illegal, the Supreme Court ruled.
Mr Johnson suspended – or prophesied – Parliament for five weeks earlier this month, but the court said it was wrong to stop MPs from fulfilling their Brexit obligations on 31 October.
Supreme Court Chief Justice Lady Hale said that "the effect on the foundations of democracy is extreme."
Downing Street said it was "currently processing a sentence".
Mr Johnson states that he wants to carry out the prophecy before the Queen's speech so that he can outline his government's new policies.
But critics said he was trying to stop lawmakers from considering his Brexit plans.
A bunch of MPs demanded the prime minister resign and Parliament to return as soon as possible.
Labor leader Jeremy Corbin said the decision showed "Mr Johnson's contempt for democracy", adding: "I urge Boris Johnson, in historical words, to consider his position."
In giving his conclusions, the Chief Justice, Haley, said: "The effect on the foundations of our democracy has been extraordinary."
She added: "The decision to advise Her Majesty to prophesy Parliament is unlawful because it has the effect of disappointing or impeding Parliament's ability to perform its constitutional functions without a reasonable justification."
Lady Hale said unanimously The jury was that Parliament was not prophesied ̵
Commons Chairman John Bercow welcomed the decision and said that Parliament "should be convened immediately", adding that it would now consult with party leaders "as a matter of urgency".
The damage is done
Aunt! It is a legal, constitutional and political dynamite.
It is only worth the breath and take into account that the highest court in the country has found the Prime Minister of the United Kingdom who acted unlawfully in the closure of a sovereign body in our constitution, Parliament, during a national crisis.
The court may not have said that Boris Johnson had an inappropriate motive for stimulating or thwarting parliamentary control, but the damage was done, he was found to have acted unlawfully and stopped Parliament from doing his work without any legal basis. .
And the court overturned both his advice to the queen and the order in the Council, which formally suspended parliament.
This means that Parliament has never been prophesied and therefore we accept that MPs are free to re-enter municipalities.
This is the most dramatic example so far of independent judges, through the mechanism of judicial review, stopping the government in its tracks because what it has done is illegal.
Ever be so powerful, the law is above you – even if you are Prime Minister.
Unprecedented, extraordinary, destructive – it is difficult to overstate the constitutional and political significance of today's decision.
What is the court thinking?
The ruling came after a three-day hearing in the Supreme Court last week that examined two complaints – one by campaigner and businesswoman Gina Miller, the second by the government.
Ms Miller appealed to the Supreme Court of England's decision that the prorogation was "purely political" and not a matter for the courts,
The Government appealed to the Court of Justice's decision at the Sessions in Scotland that the prorogation was "illegal" and was was used to "stimulate" Parliament.
The Court ruled in favor of Ms Miller's appeal and against the Government.
How do those involved react?
Speaking outside court, Ms Miller stated that the decision "spoke a lot".
"This Prime Minister must open the doors of Parliament tomorrow. Deputies must come back and be bold and daring to run this unscrupulous government at the expense," she added.
Joanna Cherry, who handled the Scottish case, called on Mr Johnson to resign as a result of the decision.
"The highest court in the United Kingdom unanimously found that his advice for prophesying to this Parliament, his advice given to her Majesty the Queen, were illegal," she said.
"His position is insolvent and he must have the insides, for once, to do the right thing and resign."
What about the other MPs?
Former Attorney General Dominic Grieve, who is an outspoken critic of the suspension, said he was "not surprised" by the ruling because of "the prime minister's rude behavior."
He told the BBC's Victoria Derbyshire program that he was "delighted" that the Supreme Court had "stopped this unconstitutional act in its tracks."
But Tory MP Andrew Bridgen said the court ruling was "the worst possible outcome for our democracy" and "absolute disgrace."
He said of the same program: "What we have is a parliament that is fully in tune with the mood of the country. They hold democracy for ransom.
" What we will see is that the president effectively takes control above Parliament and playing the tune of the remnants until October 31st. "
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