The British Supreme Court has ruled the government must seek parliamentary approval before formally initiating the process to leave the European Union.
Tuesday’s decision, which affirms an earlier High Court ruling, is a setback for Prime Minister Theresa May, who intends to invoke Article 50 of the Lisbon Treaty to leave the bloc by the end of March this year.
The UK’s 11 most senior judges voted by eight to three to reject the government’s appeal against the earlier ruling.
The ruling means May must put legislation forward to initiate Brexit to MPs for approval, a vote she would almost certainly succeed in passing as the leader of the opposition Labour Party, Jeremy Corbyn, is expected to order his MPs to vote in support of it.
The judgement will not give MPs an opportunity to stop Brexit from happening but will give them more influence on the negotiations, according the University of Surrey’s Simon Usherwood, a specialist on movements that oppose the EU.
“Losing in the Supreme Court isn’t going to change the complexity, but it might change the outcome,” he told Al Jazeera.
“Despite the broad support for EU membership among MPs, I don’t think that will translate into any particular protection of single-market membership since many MPs will fear that their constituents will see that as trying to get around the referendum result.”
The court also ruled that the government need not consult devolved parliaments in Scotland, Wales and Northern Ireland.
In Scotland, the ruling Scottish National Party had coupled its concerns over Brexit with threats to hold a second referendum to secede from the UK.
In Northern Ireland, tensions centre on the region’s future relationship with the Republic of Ireland, and the potential introduction of a border between the two, a move opposed by most politicians across the sectarian divide.
The British government has struggled to outline its terms for negotiating its exit from the EU after the unexpected vote to leave in June last year.
In opting for a so-called hard Brexit, May’s government faces the prospect of hammering out countless agreements on freedom of movement, trade, and the status of EU and British citizens living in each other’s territory.
Earlier this month, the British ambassador to the EU, Ivan Rodgers, resigned in opposition to the government’s handling of Brexit, warning it may take up to 10 years to complete.
Once the decision to leave the EU is formally invoked, negotiations between the UK and the EU must conclude within two years.