Legal challenges to a no-deal Brexit centre on political matters which must be kept outside judicial examination, the High Court in Belfast has ruled.
A senior judge has rejected all grounds of challenge to British Prime Minister Boris Johnson's strategy for taking the UK out of the EU, including claims that it would threaten the Northern Ireland peace process.
Lord Justice Bernard McCloskey delivered his ruling on Thursday morning.
Dismissing cases brought by victims campaigner Raymond McCord and two other applicants, Lord Justice McCloskey held that they were non justiciable.
According to his determination the actions indisputably focused on political issues, and targeting unpredictable and rapidly evolving government policy at national and international levels.
"Within the world of politics the well recognised phenomena of claim and counter-claim, assertion and counter-assertion, allegation and denial, blow and counter-blow, alternation and modification of government policy, public statements, unpublished deliberations, posturing, strategy and tactics are the very essence of what is both countenanced and permitted in a democratic society," he said.
Lord Justice McCloskey declared, "Considered in their totality (the applicants challenges) point inexorably to the conclusion that these cases trespass upon the prohibited domain of the non-justiciable.
"They qualify to be dismissed on this ground alone."
His decision underpins a verdict reached by senior English judges in a separate challenge over Mr Johnson's decision to suspend parliament for five weeks ahead of the October 31 Brexit deadline.
But with a Scottish court ruling that the Prime Minister acted unlawfully over the prorogation move, the Supreme Court in London will sit next week to clarify the legal position.
Meanwhile, Mr McCord pledged to seek an urgent appeal in his failed bid to secure a judicial review.
He insisted that his claims about the legality of the parliamentary shutdown was not dealt with at the case heard in Belfast.
The campaigner - whose son was murdered by loyalist paramilitaries in 1997 - said, "I am determined to take my case to the Supreme Court.
"Northern Ireland's voice must be heard at the highest court in the land because Brexit is going to affect us worse than the rest of the UK.
"As well as the potential return to violence we are now seeing reports about the impact on business.
"The chaos being predicted is going to hit everybody, not just the people who voted to remain."
In his case Mr McCord alleged that a no-deal Brexit will plunge Northern Ireland into turmoil and economic misery.
According to his legal team the government are unlawfully trying to quit the EU without an agreement at any costs.
They claim that such a departure breaches the European Union (Withdrawal) Act 2018 which safeguards the 1998 Good Friday Agreement. Counsel for the Prime Minister and UK government argued, however, that the courts should not even be dealing with issues of foreign affairs and international relations.
It was also contended that Brexit laws impose no obligation on the UK to negotiate a withdrawal agreement with the EU.
Backing the government position, Lord Justice McCloskey said: "Virtually all of the assembled evidence belongs in the world of politics, both national and supranational."
- Video report by Correspondent Jane Loughrey