A cross-community group comprising politicians, including former Justice Minister David Ford and human rights activists is to bring a legal challenge to the UK's withdrawal from the European Union (EU).
Lawyers have already written to Prime Minister Theresa May urging her to consider the country's peace process and other requirements before triggering the mechanism to leave the EU.
Despite a majority in the UK supporting Brexit in June's referendum, 56% of those who voted in Northern Ireland opted to remain.
Solicitors have threatened to take a judicial review before the High Court in Belfast - and ultimately to Europe's highest court - unless Mrs May addresses legal obligations they say she must meet, including gaining the consent of the Stormont Assembly.
They said: "These obligations include safeguarding the unique requirements of Northern Ireland constitutional law and statute, in particular the statutory recognition of the Belfast-Good Friday Agreement and satisfying the requirements of EU law incorporated into the law of Northern Ireland".
The Prime Minister and Northern Ireland Secretary James Brokenshire have been asked to respond within two weeks.
Others supporting the warning letter include: Green Party leader Steven Agnew; Social Democratic and Labour Party leader Colum Eastwood; senior Sinn Fein Stormont Assembly member John O'Dowd; former head of the Progressive Unionist Party Dawn Purvis; ex-Equality Commission member and disability rights activist Monica Wilson OBE and the the Committee on the Administration of Justice human-rights group.
They want to ensure the Brexit process complies with the rule of law, takes account of parliamentary sovereignty, protects progress made towards a more peaceful society and accords adequate weight to the democratic will of those in Northern Ireland who voted in the European referendum and in the 1998 poll on the Good Friday Agreement.
The lawyers said parliamentary legislation should authorise the triggering of the Article 50 leave clause and that law should require the consent of the Northern Ireland Assembly.
They warned if the UK Government failed to adopt a comprehensive process complying with constitutional requirements they would seek a judicial review and referral of questions surrounding EU law to the Court of Justice of the EU.