Both Sinn Fein and the Irish government have slammed a Belfast court judgment that people born in Northern Ireland are legally British not Irish
unless they renounce their British citizenship.
Sinn Fein described the court ruling as "trampling over the Good Friday Agreement".
The judges found that the relevant act was the British Nationalities law and that had not been replaced by the Good Friday Agreement in legal terms. The Good Friday Agreement allowed for residents of Northern Ireland to choose Irish or British citizenship but the British government never gave it the force of law.
"This decision from the court today is a disgracefully retrograde step," Mary Lou McDonald, Sinn Fein president said. 
Foreign Minister Simon Coveney also voiced his anger at the finding that people born in Northern Ireland are automatically British.
Irish deputy leader Simon Coveney.
Irish deputy leader Simon Coveney.
"Citizenship and Identity provisions are critical to the Good Friday Agreement (GFA)," he said.
"The UK Govt has pledged to review rules around citizenship and deliver a long-term solution consistent with GFA. An outcome is urgently needed and I will raise this again with Secretary of State for Northern Ireland tomorrow."
The case involved Emma DeSouza, from Magherafelt, Co Derry, who applied for a residence card for Northern Ireland for her US-born husband Jake. She identified herself as an Irish citizen.