A legal challenge over Brexit is coming before the High Court for the first time.
The case is being brought by British citizen Deir Dos Santos in a bid to prevent the Government from triggering Article 50 of the Lisbon Treaty without the prior authorisation of Parliament.
Two senior judges in London are expected to set down a timetable on Tuesday for a judicial review hearing later in the year on Article 50, which will start the formal process for Britain's departure from the EU.
The application has been described by lawyers involved as "the most important constitutional law case in living memory".
Sir Brian Leveson, president of the Queen's Bench Division, and Mr Justice Cranston will also be considering related Article 50 challenges that are pending.
The Dos Santos case is being led by international law expert Dominic Chambers QC, instructed by law firm Edwin Coe, which says the challenge concerns the sovereignty of Parliament.
Among the key issues judges will have to analyse at the full hearing is the true extent of the Prime Minister's executive powers.
The Government is expected to assert that the royal prerogative can be used to trigger Article 50.
David Greene, senior partner and head of group action litigation at Edwin Coe, said: "Whilst Brexit is highly political, the issue before the court tomorrow is a basic question of the rule of law.
"The claimant submits that the course proposed by the Government is unlawful because only Parliament is empowered to authorise service of the Article 50 notice and consequent withdrawal from the EU.
"The Government asserts that the executive may use the royal prerogative to serve the notice. The court is asked to determine that issue in isolation from the politics that surround the whole question of Brexit."