Can the Theresa May government trigger Article 50 of the Lisbon Treaty to begin the process of leaving the European Union without MPs passing a new law to that effect in parliament?
This was the key question as the packed high court began hearing a case on Thursday that is likely to have far-reaching effects on British politics and constitutional law. As Brexit-related moves gather pace, attention is focused on the case that is expected to reach a judgement on Monday.
The case is seen as an attempt by those opposed to Britain leaving the EU to negate the June 23 referendum vote to leave the bloc. Three of the most senior judges, Baron Thomas of Cwmgiedd, the Lord Chief Justice of England and Wales, Terence Etherton and Lord Justice Sales, are hearing the challenge.
In opening arguments over who should initiate Britain’s exit from the EU, Lord Pannick, who represents the lead challenger in the claim, Gina Miller, said formal notification by ministers alone would undermine Parliament and “deprive people of their statutory rights”.
Pannick told the court: “Notification is pulling the trigger and once pulled the bullet hits the target. It inevitably leads to the consequence that the (European Communities Act 1972) ceases to apply. This is not simply action on the international plane…It leads to the removal of a whole series of important rights whatever Parliament may think about it later.”
The government, he said, was wrong to suggest the legal challenge “was merely camouflage” to prevent Brexit, and added that Miller “is entitled to require that the steps that will be taken must be taken in a lawful manner”.
Outside the court, pro-EU supporters were draped in EU flags, while opponents handed out leaflets saying “Invoke Article 50 now”.