The court heard that the Northern Irish people have "control over constitutional change"
Lawyers representing a group of people against Brexit say Northern Ireland could veto withdrawing from the EU.
A cross-community group of politicians and victims campaigners is challenging British prime minister's Theresa May's ability to trigger Article 50 negotiations on an exit at the High Court in Belfast.
A solicitor at the High Court in Belfast today said it cannot be imposed upon people in the North.
Ronan Lavery QC, quoted by The Guardian, said: “Sovereignty over constitutional affairs has been ceded [by the UK]. It is not the relationship, as it might once have been, between a dominant partner and a submissive partner.
“The people of Northern Ireland have control over constitutional change - it cannot be imposed upon the people of Northern Ireland. If that means that Northern Ireland could exercise a veto over withdrawal then I am [asserting] that is what Britain signed up to when it signed the Good Friday agreement.”
Sinn Féin's John O'Dowd is supporting the legal action.
He suggested that the referendum would have a "huge impact" on the Good Friday Agreement.