Mr Justice Liam McKechnie made his ruling under the European Convention on Human Rights but he suggested it was time for a change to domestic Irish law which is guided by the constitutional bias against unmarried fathers.
The judge made his comments in a 62-page ruling in the case.
One in three children in Ireland are born to unmarried parents yet, unlike the mother or a married man, the Constitution gives the unmarried father no automatic legal status in the lives of his children. He only attains legal status if he makes a formal application for guardianship.
Mr Justice McKechnie said he did not challenge the constitutional principle that fathering a child should not automatically confer rights on the father as there were many cases where fatherhood was due to a one- night stand, rape or incest.
“But what about a person who fathers a child within an established relationship, and who from the moment of birth, nurtures, protects and safeguards his child, to a standard which all too frequently married fathers fail to live up to?” he said.
The judge said such relationships had nearly all the characteristics of a constitutionally protected family. “Could I respectfully suggest that our society, which is governed by a Constitution which declares the principles of prudence, justice, charity and human dignity, might in its maturity so agree?”