The Nigerian mother of an Irish-born baby today began a High Court challenge against an order to deport her.
Ms Bola Funni Ojo is believed to be the first to challenge deportation which was made possible by a recent court decision.
It was ruled in the Supreme Court that having Irish children was not a basis for non-nationals to stay in the country.
Ms Ojo and her six-week-old son have been detained at a centre at Mountjoy Prison since the end of January.
The High Court heard that she had to leave her four-year-old daughter in the care of her friend in Waterford City, where she was living before.
Ms Ojo is challenging the State's refusal to allow her the right to reside in Ireland and is applying for a declaration that her arrest and the detention of her son were unlawful.
Under rules that come into effect last week immigrant parents can no longer seek residency in Ireland on the basis of having Irish-born children.
Last month's Supreme Court judgment ruled that non-EU immigrant parents no longer had an automatic right to remain in the Republic.
Ireland's Minister for Justice, Mr Michael McDowell, ruled out mass deportations of people whose applications are being processed, saying cases would be handled individually.
He also indicated that the length of time the parents of Irish children have lived in the State would be a key factor in considering applications.
Ms Ojo is claiming Mr McDowell's decision was biased and ill-considered, and criticised the speed and manner in which it was made.
She said she had to flee Nigeria because her life was in serious danger. She was refused refugee status upon entering Ireland.
PA