Three separate legal challenges have been lodged in Belfast against a potential no-deal Brexit.
The High Court proceedings centre on claims that any departure from the European Union without a withdrawal agreement would breach the Belfast Agreement.
Lord Chief Justice Sir Declan Morgan listed one of the actions, brought by victims campaigner Raymond McCord, as the lead case for hearing next month.
With the challenges expected to go all the way to the Supreme Court, efforts are being made to ensure a final determination can be made before the UK intends to quit the EU on October 31st.
Mr McCord said his bid to judicially review British prime minister Boris Johnson was about ensuring the relative peace in Northern Ireland is not jeopardised.
“This is important for both Remainers and Brexiteers; you can’t have one person and his cabinet deciding to ignore the democratic system,” he said outside court. “It could affect the Good Friday Agreement, which has given us relative peace since 1998, and I certainly don’t want to go back to the really bad days.
“Let’s ensure we don’t have a hard border, but let’s do it in a democratic way.”
Separate grounds of challenge aimed at preventing Mr Johnson suspending parliament to force through a no-deal Brexit will now be dealt with in another case taken in Scotland by a cross-party group of MPs and peers.
Mr Johnson has pledged the UK will leave the EU on October 31st, “do or die”.
Mr McCord's lawyers wrote to the prime minister seeking assurances before commencing judicial reviews proceedings. They now want a court declaration that exiting without an agreement would be contrary to the Northern Ireland peace process.
His solicitor, Ciaran O’Hare of McIvor Farrell, said this was a key case.
"My client's case is that a no-deal Brexit will be an unconstitutional assault upon the good people of Northern Ireland and will inevitably lead to the demise of the United Kingdom of Great Britain and Northern Ireland, driving Northern Ireland into the arms of the Republic of Ireland," Mr O'Hare said.
“He is of the view that it is unconstitutional for the government and the prime minister of the United Kingdom to take steps which are clearly not in the national interest at the enormous expense, hardship and suffering of the people of Northern Ireland, an equal partner in the union.”