Government urges Supreme Court to overturn 'wrong' Brexit ruling
The Government has urged the UK's highest court to overturn a ruling that the Prime Minister must seek MPs' approval to trigger the process of taking Britain out of the European Union.
Eleven Supreme Court justices - a record to hear an appeal - are hearing the challenge over the country's Brexit strategy, which has attracted worldwide attention from media and public.
The hearing will be the most televised UK case ever, with the proceedings streamed on the Supreme Court website and broadcast on television.
In a decision on November 3 that infuriated Brexiteers, three High Court judges said Theresa May lacked power to use the royal prerogative to trigger Article 50 of the Lisbon Treaty and start the two-year process of negotiating Brexit without the prior authority of Parliament.
Now the justices are to have their say regarding one of the most important constitutional cases in British legal history.
The Government's top law officer, Attorney General Jeremy Wright, told the justices that the case was of "great constitutional significance in which there is understandable and legitimate interest both inside and outside this courtroom".
"Secondly, in the light of what followed the Divisional Court (High Court) judgment, it should be said with clarity this is a case which the claimants brought perfectly properly and which it is now perfectly proper for this court to decide."
Mr Wright said the High Court had reached the "wrong" decision. It was for the Government to exercise prerogative powers in the conduct of the UK's affairs on the international plane.
He told the judges that triggering Article 50 "will not be an exercise of the prerogative right on a whim or out of the blue", but was part of a process in which "Parliament has been fully and consciously involved".
Mr Wright said the use of the prerogative in the circumstances would be lawful. The prerogative was not "an ancient relic", but a "constitutional necessity".
He said the legislation enabling the EU referendum had been passed with the "clear expectation" that the Government would implement the result.
James Eadie QC, also representing the Government, described the prerogative as "a long-standing, well-recognised set of powers firmly established in our constitutional arrangements" which were "fundamental to our constitution and essential to effective government".
If the appeal is unsuccessful, and any potential further appeal to the European Court of Justice in Luxembourg also fails, the Government's plans for Brexit could be thrown into disarray.
But Mrs May has made it clear she still intends to give an Article 50 notification by the end of next March to start the leave negotiations with 27 other EU countries.
At the outset of the hearing Lord Neuberger, the court's president, said all parties had been asked whether they wished any of the judges to stand down. He said that all parties to the appeal had stated that they have no objection to any of the justices sitting on the appeal.
The announcement follows media reports and comments questioning the independence of members of the judiciary.
Brexit Secretary David Davis is leading the Government's historic legal action. His team of lawyers, headed by Mr Wright, will argue in the four-day hearing that the three High Court judges erred over Article 50 and its use was legally justified by the June 23 referendum vote in favour of quitting the EU.
The High Court ruling was won by Gina Miller (51), who was selected to bring the lead case.
The Scottish and Welsh governments and the Attorney General for Northern Ireland are all intervening in the Supreme Court case.
A ruling will not be given until the new year.