Brexit legal challenge begins at UK high court

Three of the most senior judges in England and Wales are set to hear claims that the government cannot trigger Brexit without parliamentary approval.

Today kicks off two and a half days of arguments at London’s Royal Courts of Justice U in a legal dispute over who has authority to notify Brussels formally that Britain is withdrawing under article 50 of the treaty on European Union (TEU).

Article 50 states that any member state may leave “in accordance with its own constitutional requirements”, an undefined term that has allowed both sides to pursue rival interpretations.

UK Prime Minister Theresa May announced at the Conservative Party conference that she intends to trigger Article 50 by the end of March next year. The government maintains that the decision to depart has been taken by the referendum on 23 June and that its executive powers, under the royal prerogative, are sufficient for David Davis, the Brexit secretary, to give notice on behalf of the cabinet.

But May is facing a legal challenge over whether the government can use a historical power known as royal prerogative, to decide when, how and whether to make this decision.

The lead case is being brought by Gina Miller, an investment fund manager and philanthropist.

David Pannick, the lawyer representing Miller, told the High Court the case raised questions of fundamental constitutional importance, saying that the government was wrong to suggest that Miller was trying to change the outcome of the referendum in which 52% voted to leave the EU and 48% to remain. The case was only about the right to invoke Article 50, he said.

"Our legal claim is in support of parliamentary sovereignty. What it does with that parliamentary sovereignty is a matter for parliament," he said, adding that parliament might approve a Bill to invoke Article 50, reject it, introduce amendments on timing or to require the government to report back to lawmakers.