UK court rules gov't cannot trigger Brexit without Parliament

Britain's High Court brought government plans for leaving the European Union screeching to a halt yesterday, ruling that the prime minister can't trigger the U.K.'s exit from the bloc without approval from Parliament. The government said it would go to the Supreme Court to challenge the ruling, which has major constitutional as well as practical implications. Britons voted by a margin of 52 to 48 percent to leave the EU, a process known as "Brexit." Several claimants challenged the plans for Brexit in a case hinging on the balance of power between Parliament and the government.

British Prime Minister Theresa May has said 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. Claimants argue that leaving the EU will remove rights, including free movement within the bloc, and say that can't be done without Parliament's approval. Three senior judges ruled that "the government does not have the power under the Crown's prerogative" to trigger the official exit process. The British government immediately said it would appeal the judgment. The government said in a statement that Britons voted to leave the bloc in a referendum approved by an Act of Parliament, "and the government is determined to respect the result of the referendum." The Supreme Court has set aside time to hear the appeal before the end of the year. The case is considered the most important constitutional matter in a generation.

May wants to use royal prerogative, historic powers officially held by the monarch, to trigger Article 50 of the EU's treaty, which starts two years of talks before Britain's departure from the EU. The powers, which have in reality passed to politicians, enable decisions to be made without a vote of Parliament and cover matters as grave as declaring war or as basic as issuing passports.