A fresh attempt to use the Irish courts to redefine marriage is set to be made by Senator Katherine Zappone and Dr Ann Louise Gilligan.
Their new case is set to challenge the Civil Registration Act 2004, and the Civil Partnership Act 2010, both of which prohibit people of the same sex marrying each other and will begin in the High Court.
The two women argue that the State's refusal to recognise their same-sex marriage, entered into in Canada, was unconstitutional but lost their case in the High Court in 2006 and subsequently took their case to the Supreme Court.
The Supreme Court has yet to hear their appeal, but last year it refused them permission to add another argument to their motion.
Dr Gilligan and Senator Zappone wanted to amend the grounds to include an argument that Section 2.2 of the Civil Registration Act 2004 was unconstitutional.
The section says there is an “impediment to marriage” if it involved two people of the same sex.
The Court said that while the 2004 Act had been noted in the original 2006 High Court decision, a full constitutional challenge had not been mounted in that court.
Zappone and Gilligan married in Canada in 2003 and had sought to have their marriage recognised in Ireland.
Article 3. 1° of the Constitution states: "The State pledges itself to guard with special care the institution of Marriage, on which the Family is founded, and to protect it against attack."