Even though the passage of the Protection of Life During Pregnancy Bill is assured, there is still at least a week of debate in Seanad Eireann on the abortion legislation, starting this afternoon.

A substantial amount of time has been allocated this week with the Seanad - very unusually - sitting on all five days. The main business on four of those days is the abortion Bill and the debate could spill into next week.

While a majority of the 60-member Upper House are expected to support the legislation, at least two – and possibly four – Fine Gael senators will join those who have lost the party whip.

That said, the Bill will be passed. There are a number of eventualities that can occur once that happens. The President has powers under Article 26 of the Constitution to refer Bills to the Supreme Court to test their constitutionality after first consulting with the Council of State. If the court upholds the constitutionality of a Bill, it can never be challenged by a citizen in court.

The power has been invoked some 15 times since the Constitution came into being in 1937, the most recent of which was a referral in early 2005 by then president Mary McAleese of the Bill the Government introduced to prevent retrospective compensations payments to residents of nursing homes and other institutions.

In 1976, then president Cearbhail Ó Dálaigh referred emergency powers legislation under Article 26. That provided the pretext for then minister for defence Patrick Donegan branding him a "thundering disgrace". The incident led to Mr Ó Dálaigh resigning from office.

Minister for Transport Leo Varadkar said last week President Michael D Higgins should refer the Bill using the Article 26 powers. However, his Labour Ministerial colleague Pat Rabbitte was decidedly more circumspect yesterday saying that he was sure Mr Higgins would rely on his own counsel on the matter.

The other distinct probability is that the Bill once enacted into law will face legal challenges from individuals or anti-abortion campaigners.

Caroline Simons of the Pro-Life Campaign has said that she believes that such an eventuality is likely. Ms Simons also said her group would like a referendum on the issue but conceded it was unlikely to happen during the lifetime of this Government.

On the other side of the argument, Mr Rabbitte all but confirmed yesterday that the Labour Party will not be pressing for any further extension to abortion laws – such as providing for fatal foetal abnormality or cases of rape or incest - during the lifetime of the coalition.