The Supreme Court, by a five-two majority, yesterday decided that non-national parents of Irish-born children and their non-national siblings are not entitled to live in this country by virtue of having an Irish-born child.
Experts believe that about 10,000 non-national adults and children could face deportation.
Yesterday's decision, upholding a High Court decision last year, directly concerns two families but will have have a knock-on effect for thousands of non-Irish- born adults and children in similar situations.
Their cases will now have to be looked at individually before decisions are made.
The High Court had upheld the making of deportation orders against a Nigerian man and a couple from the Czech Republic and their non-national children. The case came before the Supreme Court by way of an appeal against the High Court decision.
The case was taken by Mr Andrew Osayande, a Nigerian and a couple from the Czech Republic, the Lobes, and their three non-Irish-born children.
The Czech couple's fourth child, a boy, was born here in October 2001. Mr Osayande's son was born here in November 2001.
Both families came here in 2001 having unsuccessfully applied for asylum in Britain. Deportation orders were made in the UK in September 2001.
The UK has agreed to deal with their applications under the Dublin Convention, a treaty between EU governments under which asylum applications are considered by the country the applicants first enter.
The Chief Justice, Mr Justice Ronan Keane, in the lead judgment dismissing the appeal yesterday, said the issue was to what extent the Irish citizenship of a child conferred an automatic right of residence on the parents and siblings of that child.
He thought it would be wrong for the court to approach the important issues which had arisen without regard to the major changes in Ireland over the past decade which had led, not merely to the enactment of legislation, but to an ever increasing volume of litigation about illegal immigrants' entitlements.
The Chief Justice said many would wish to see the development in Ireland of a tolerant and pluralist society which accommodated immigrants from diverse ethnic and cultural backgrounds because that was a desirable objective in itself. This recognised the openness and generosity Irish emigrants had received in the past and, on a purely economic level, remedied a serious shortage in the labour markets.
At the same time, the legislature and Executive could not be expected to disregard the problems which an increased volume of immigration inevitably created because of the strains it placed on social services and, human nature being what it was, the difficulty of integrating people from different ethnic and cultural backgrounds into the fabric of Irish society.
The resolution of the complex political, social and economic issues surrounding immigration, which were not unique to Ireland, was entirely a matter for the Oireachtas and the Executive. The court's function was to ensure that the constitutional and legal rights of all persons affected by the legislation were protected and vindicated.
The Chief Justice said the present case was distinguishable from the Fajujonu case of 1990.
The factual and statutory context in which the Minister was required to decide on a deportation order had altered radically since then.
Those who agreed the appeal should be dismissed were Mrs Justice Susan Denham, Mr Justice John Murray, Mr Justice Adrian Hardiman and Mr Justice Hugh Geoghegan.
In the minority were Mrs Justice Catherine McGuinness and Mr Justice Nial Fennelly.
Mrs Justice Denham said if the Minister was satisfied the common good required that the residence of the parents within the State should be terminated, even though this meant that to remain a family unit the child who was an Irish citizen would have to leave the State, then that was an order he was entitled to make.
Mr Justice Murray said that in the circumstances of the case, he was satisfied the Minister's decision had been shown to be reasonable and rational in determining there existed good and sufficient reasons associated with the common good for the making of deportation orders.
Mr Justice Geoghegan said the appellants had relied heavily on the Fajujonu case. Little or no significance should be attached to the particular facts of that case in discerning the principles which the court had enunciated here.
Mr Justice Hardiman said that in addition to policy considerations to be derived from the statutes and other instruments cited, a Department official had stated there had been a dramatic increase in the numbers seeking asylum here since 1995 and a significant increase in the number of applications for residency on the basis of parentage of an Irish-born child.
From the figures, it would appear leave to remain here had in fact been granted over a period of years to a significant number of relatives of Irish-born children.
Dissenting judge Mr Justice Fennelly said it would be seen that it was perfectly possible for the State to examine the present applications in accordance with the terms of the Dublin Convention.
He did not think that the application of the Dublin Convention furnished a sufficiently powerful reason to justify the Minister in deporting the parents of the Irish-born children in the present cases.
Mrs Justice McGuinness, also dissenting, referred to the repeated emphasis by the Supreme Court over the years on the nature, weight and importance of the rights of the family set out in Articles 41 and 42 of the Constitution. The Minister accepted the present children and their families had those rights.
She was not satisfied that respect for the maintenance of the immigration and asylum system was sufficiently grave and substantial a reason, or so predominant and overwhelming a reason, to justify the denial of the constitutional rights of the children and their families.