In a move that will come as a blow to the UK government, Britain’s Supreme Court ruled on Tuesday that Parliament must be given the power to decide whether the country can begin its two-year exit strategy from the European Union.

The ruling comes after Prime Minster Theresa May and her Conservative government appealed a High Court ruling in November, which said that the government alone cannot trigger Article 50 of the Lisbon Treaty – the formal notification of the UK’s intention to leave the European Union – without a Parliamentary vote.

Tuesday’s ruling means that May cannot begin negotiations with the EU until Members of Parliament and peers give their backing. But before anti-Brexit camps get too excited, May and her party are expected to get backing in time for the government’s March 31 deadline. While it’s a landmark case, it looks to be merely a setback for May, who last week unveiled her 12-point Brexit strategy and confirmed that the UK would absolutely leave the EU’s single market.

During the ruling from the Supreme Court – Britain’s highest court –, campaigners said denying Parliamentary say in Brexit was undemocratic.

Supreme Court President Lord Neuberger said: “By a majority of eight to three, the Supreme Court today rules that the government cannot trigger Article 50 without an Act of Parliament authorising it to do so.”

Attorney General Jeremy Wright said that the government was “disappointed” but would “comply” with the court’s ruling.

Gina Miller, who brought the case against the government told reporters outside of the court that the Brexit judgement “is about legal process not politics.”

Jeremy Corbyn, leader of the Labour party (the government’s opposition) said that his party “respects the result of the referendum and the will of the British people and will not frustrate the process for invoking Article 50.”

Mid-morning trading saw the pound slip back slightly to $1.2491, down from a day high at $1.2548. It had climbed to a five-week high on Monday after Donald Trump’s confrontational start to his presidency stung the U.S. dollar.

In June, the UK voted to leave the EU by a margin of 51.9% to 48.1%, a move which sent fear through the entertainment industry over what Britain’s future role would be. Having it as part of the EU offers benefits to global players and their access to Euro markets and the drop in pound Sterling has affected box office receipts for U.S. studios in the UK. However, Britain has become a much more attractive place for productions looking to shoot in the territory thanks to this and the country’s generous tax credit.