LONDON (AFP) - The High Court in Belfast will rule Friday (Oct 28) on Northern Ireland's entitlement to veto Britain's departure from the European Union - the first opinion by a British judge on Brexit.
With other legal challenges under way in Britain, the outcome will be closely monitored by politicians and financial markets.
A cross-party group of politicians, including members of the British province's largest Irish nationalist parties, brought the challenge earlier this month, arguing that a vote in the Northern Ireland regional assembly should also be required.
Ciaran O'Hare, a lawyer representing veteran victims' rights campaigner Raymond McCord - one of a diverse group of individuals in the case - said the judge would give his ruling at 0900 GMT Friday (5pm Singapore time), after three days of hearings earlier this month.
"We are delighted at such a quick turnaround but time is obviously of the essence," O'Hare said.
He described the ongoing legal challenge as "a David versus Goliath battle" that would not end on Friday regardless of the outcome.
"Both sides will likely appeal to the Supreme Court but the ruling in Belfast is important because it would have to be taken into account," he said.
The campaigners argue Brexit cannot be imposed on Northern Ireland because the 1998 Good Friday Agreement, an international treaty involving the neighbouring Republic of Ireland, gives Northern Ireland residents control over future constitutional change.
"The historical context is vital in our case: we believe the Good Friday Agreement gives us a veto," O'Hare said.
In the June 23 referendum on EU membership, Northern Ireland voted 56 per cent in favour of the British staying in the bloc, while across the entire kingdom, 52 per cent voted to leave.
McCord has joined the cross-party group taking the case, warning that the loss of EU funds could undermine the Northern Irish peace process, which is underpinned by the Good Friday Agreement.
"The EU has pledged funding until at least 2020 but the British government has given no undertaking it will continue to fund projects to bring the two communities together," he told AFP at an earlier hearing.
Under the EU programme for peace and reconciliation in Northern Ireland, the province will receive a total of 229 million euros (S$357.9 million) in funding by 2020 for initiatives regarded as crucial for building bridges across the sectarian divide in the region.