Four day debate Five months after United Kingdom's referendum to abandon the European Union, the question of who actually gets to pull the trigger on Brexit remains a muddle. Prime Minister Theresa May says she does. A high-level British court argued otherwise last month, ruling that Parliament must have a say. Now it’s up to the U.K. Supreme Court, which this week began hearing arguments in a case that could complicate May’s plan to set in motion Britain’s exit by the end of March.