The UK’s High Court has ruled that Theresa May’s administration is not allowed to trigger the country’s exit from the European Union, or Brexit, without approval from parliament. Three senior judges ruled on Thursday that “the government does not have the power under the Crown’s prerogative” to start EU exit talks, Al Jazeera reported. The government plans to appeal against the ruling before the Supreme Court. Plans for Brexit are being challenged in a case with major constitutional implications, hinging on the balance of power between parliament and the government. May has said that she will launch exit negotiations with the EU by March 31. She is relying on a power called the royal prerogative that lets the government withdraw from international treaties.