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 — the legal mechanism that begins the process of leaving the EU — by the end of March.
Doing so will open the door for EU negotiations, which are likely to last two years.
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.
May became UK Prime Minister following David Cameron’s resignation, after failing to secure enough votes to remain in EU.