Opposing the couple's application, Jeremy Maher SC, for the State, said that while the historical background to the case, which dated back to the marriage laws enacted during the reign of Henry VIII, was "interesting", the real issue was the constitutionality of the 1907 and 1921 Acts, he said.
The laws were presumed constitutional and were enacted in the interest of the common good and to protect the institutions of marriage and the family, he said. The courts had held the family is that which is based on marriage.
Marriage has judicially been held to be a lifelong commitment and, for that to be the case, it needed to be given security and stability, counsel argued. Marriage provided for the coming together of two separate families and it was understood that the relationship between the partners in a marriage with the siblings of their spouse would be non-sexual. A person who married accepted their spouse's family as if they were their own until death.
The essential difference between death and divorce is that death is a natural and permanent process which cannot be controlled, counsel said. Divorce, however, was brought about and was therefore an artificial state of affairs. The disputed laws represented an entirely proportionate response of the legislature to the necessity of protecting the institution of marriage and forbidding the development during marriage of a sexual relationship with a spouse's sibling.
The prohibition on such marriages was also necessary to protect children, Mr Maher argued. If such marriages were permissible, it would expose children to undue confusion, hurt and turmoil and also present problems for the parents of persons who wished to engage in such marriages.
While the right to marry was a fundamental right, it was not absolute and could be delimited in the public good, he said.