When will the Supreme Court announce its decision?

The Supreme Court will rule at 9.30am on Tuesday whether Theresa May has sufficient authority to withdraw the UK from the European Union, or if parliament must have a say in her plans.

The judges, who are the most senior in the country, will deliver their verdict on whether MPs are entitled to a vote on whether the Prime Minister triggers Article 50, the formal mechanism by which EU withdrawal can commence.

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What are the two sides arguing over?

Speaking on behalf of Ms May, government lawyers have argued the referendum of 23 June, in which a slim majority voted for Brexit, means she has sufficient mandate to act. They also argued that Prime Ministers have traditionally acted to sign international treaties or agreements with other countries, without approval from parliament.

However, those taking the case against the government have argued Ms May requires the approval of parliament before she can act. They have claimed that under constitutional law, only parliament can be responsible for taking away the rights of citizens. As cessation of EU membership would result in the loss of certain rights such as freedom of movement, or the right to vote in EU elections, British citizens will lose rights in this instance and so only parliament can enact Brexit, their lawyers told the court.

Supreme Court Brexit Challenge Show all 13 1 /13 Supreme Court Brexit Challenge Supreme Court Brexit Challenge People wait to enter the public gallery outside the Supreme Court ahead of the challenge against a court ruling that Theresa May's government requires parliamentary approval to start the process of leaving the European Union, in Parliament Square, central London Reuters Supreme Court Brexit Challenge Gina Miller, co-founder of investment fund SCM Private arrives at the Supreme court in London on the first day of a four-day hearing Getty Supreme Court Brexit Challenge A man waves the EU flag in front of the Supreme Court Getty Supreme Court Brexit Challenge Satirical artist Kaya Mar poses with two of his paintings in front of the Supreme Court Getty Supreme Court Brexit Challenge Pro-Europe protestors dressed as Supreme Court Justices stand outside the Supreme Court ahead of the first day of a hearing into whether Parliament's consent is required before the Brexit process can begin. The eleven Supreme Court Justices will hear the government's appeal, following the High Court's recent decision that only Parliament can trigger Article 50 Getty Supreme Court Brexit Challenge The eleven Supreme Court Justices will hear the government's appeal, following the High Court's recent decision that only Parliament can trigger Article 50 Getty Supreme Court Brexit Challenge Businesswoman Gina Miller arrives at the Supreme Court ahead of the first day of a hearing into whether Parliament's consent is required before the Brexit process can begin Getty Supreme Court Brexit Challenge Attorney General Jeremy Wright arrives at the Supreme Court in London EPA Supreme Court Brexit Challenge Protesters outside the Supreme Court in London, where the Government is appealing against a ruling that the Prime Minister must seek MPs' approval to trigger the process of taking Britain out of the European Union PA wire Supreme Court Brexit Challenge A protesters wearing a judge's wigs and robes stands outside the Supreme Court ahead of the challenge against a court ruling that Theresa May's government requires parliamentary approval to start the process of leaving the European Union, in Parliament Square, central London Reuters Supreme Court Brexit Challenge A protester holds up a placard outside the Supreme Court ahead of the challenge against a court ruling that Theresa May's government requires parliamentary approval to start the process of leaving the European Union, in Parliament Square, central London Reuters Supreme Court Brexit Challenge Pro-Europe protestors dressed as Supreme Court Justices stand outside the Supreme Court Getty Supreme Court Brexit Challenge A man waiting to enter the public gallery waves a European Union flag outside the Supreme Court ahead of the challenge against a court ruling that Theresa May's government requires parliamentary approval to start the process of leaving the European Union, in Parliament Square, central London Reuters

Who has brought the case forward?

The case is brought against the government by a number of parties, including Gina Miller, a philanthropist and former investment banker. She is also joined by a crowd-funded initiative known as the People’s Challenge, comprised of pro-EU “concerned citizens”.

The legal challenge first went to the High Court in November, where judges ruled against the government and found parliamentary approval must be sought. However, the government appealed the verdict, whereupon the case was referred to the Supreme Court.

Upon appeal, applicants from Northern Ireland were also allowed to join the case in order to make their argument that leaving the EU without consulting the Stormont parliament may be a violation of the Good Friday Agreement, the peace treaty which ended the Troubles conflict.

Who is expected to win the case?