LONDON (CNN) — Britain’s Supreme Court has ruled that the UK government must hold a vote in parliament before beginning the process of leaving the European Union.
The decision is a complication for Prime Minister Theresa May, who wanted to trigger Article 50 of the Lisbon Treaty — the legal mechanism that begins the process of leaving the EU — by the end of March. Doing so would open the door for EU negotiations, which are likely to last two years.
The Supreme Court judges voted eight to three against the government, saying that the legal consequences of leaving the EU were great enough to require an act of parliament to start the process.
“To proceed otherwise would be breach of settled Constitutional principles stretching back many centuries,” Lord David Neuberger, president of the Supreme Court, said as he read out the ruling.
But the court decided that the UK government did not need the approval of devolved governments in Scotland, Northern Ireland and Wales to begin the negotiating process.
May has promised lawmakers a vote on the outcome of the talks, but wanted to begin the process without a decision in parliament. The government must now introduce legislation to the House of Commons, which could delay May’s timetable.
The government had appealed a November High Court decision and Supreme Court judges deliberated the case over four days in December before giving their verdict Tuesday.