The Government could introduce same-sex marriage without having a referendum, a legal academic has claimed.
Writing in yesterday's Irish Times, Dr Conor O'Mahony of UCC said that the Constitution was silent on same-sex marriage, and that it therefore presented no bar to the Government introducing same-sex marriage legislation.
His view contrasts with the opinion of a range of members of the Government, notably Taoiseach Enda Kenny and Education Minister Ruairi Quinn, who have said that a referendum would be needed.
Mr Quinn said that the Constitution defined marriage as being between a man and a woman. In fact, the Constitution does not explicitly define marriage in this way, but case law has always understood it to mean this.
Dr O’Mahony said: “The stumbling block identified by all parties is the Constitution, which in Article 41.3 pledges the State to “guard with special care the institution of marriage, on which the family is founded, and to protect it against attack”.
“Nothing in this sparse text defines marriage as one man and one woman, and the equality guarantee suggests limiting access to marriage on grounds of sexual orientation is discriminatory.”
While he acknowledged that same-sex marriage “was clearly not contemplated when the Constitution was drafted in 1937” he said that it had “always been accepted by Irish courts that the Constitution, with its vague language, is to be interpreted in light of conditions in society today, and not by reference to opinions and standards in 1937”.
The only case to have considered same-sex marriage, he said, was Zappone and Gilligan v Revenue Commissioners. However he claimed that judgment “was unclear as to whether the term 'marriage' in the Constitution is inherently opposite-sex”.
One passage in the judgment suggested that the Constitution defined marriage as opposite sex, “but another suggested the key factor was consensus in society today, as represented in the most recent legislation on the point,” he added.
In her judgment, Justice Elizabeth Dunne cited Hamilton C.J in the case T.F. V Ireland, where he said:
“As to how marriage should be defined, the Court adopts the definition given by Costello J. in Murray v. Ireland  I.R. 532 at p. 535: ‘…the Constitution makes clear that the concept and nature of marriage, which it enshrines, are derived from the Christian notion of partnership based on an irrevocable personal consent, given by both spouses which establishes a unique and very special lifelong relationship’.”
Justice Dunne went on to say: "Marriage was understood under the 1937 Constitution to be confined to persons of the opposite sex. That has been reiterated in a number of the decisions which have already been referred to above, notably the decision of Costello J. in Murray v. Ireland . The Supreme Court decision in T.F. v. Ireland and the judgment of Murray J. in T. v. T ........ That has always been the definition.
"In this case the court is being asked to redefine marriage to mean something which it has never done to date."
Dr O'Mahony acknowledged that courts were “reluctant to interfere in matters that are the subject of intense political controversy, and the fact that this issue has been referred to the constitutional convention means a court decision in favour of same-sex marriage could be seen as subverting democracy”.
But he claimed what he called a “compromise” position would be “to say that while the vague provisions of Articles 40 and 41 of the Constitution do not guarantee same-sex marriage, they equally do not preclude it – the choice is a matter for the Oireachtas, which is free to reflect changing consensus in society by legislating for same-sex marriage without a referendum”.
He said: “In light of the prevailing mantra about the limitations imposed by the Constitution, no government is likely to test this view by enacting such legislation in the absence of a court decision first clarifying the exact position.”