The Welsh and Scottish governments will have the right to influence the Supreme Court decision on how Brexit should be activated.
The U.K. government is making an an application to review a High Court ruling that MPs must vote on triggering Article 50.
The Supreme Court stated that Scotland and Wales’ highest ranking law officers will be permitted to take part in the appeal.
Prime Minister Theresa May said that work was “on track” on Friday to begin the formal process of Brexit before April 2017.
At a shared press briefing with Chancellor Angela Merkel, after a meeting with EU leaders in Berlin, Mrs May said: “We stand ready to trigger Article 50 by the end of March 2017 and I want to see this as a smooth process, an orderly process, working towards a solution that’s in the interests of both the UK and also in the interests of our European partners.”
Mrs May was speaking after the Supreme Court confirmed that Scotland’s highest law officer, the Lord Advocate, had been invited to address the court on the relevance of points of Scots law. The Counsel General for Wales will make arguments about the significance of parliamentary sovereignty and the rule of law.
The Supreme Court hearing is predicted to start on 5 December and go on for four days, with the decision expected early next year.