1. There was no vote on the Lisbon Treaty (or any other treaty). There was a vote to amend the constitution to facilitate ratification and to add in extra lines into the constitution (a wording BTW
FF entirely fukked up. A first year law student could have come up with a better draft to achieve the same effect!).
2. The role of ratifying treaties is ALWAYS a matter for the Oireachtas. All the amendment was, was an enabling provision. Treaties are always ratified by parliaments. (BTW the Oireachtas some weeks ago ratified another EU treaty.)
3. There is a strong legal case for saying that neither Lisbon, nor Nice, nor Amsterdam ever needed constitutional amendments, and hence referenda. It appears that successive governments have taken
political decisions to amend the constitution when they were not needed.
In other words, legally there is no reason why the Oireachtas cannot ratify the treaty. It might perhaps do it using Article 26 to be certain.
The issue is whether politically it should do so. The problem Ahern/Cowen created is that they chose a referendum route when the belief is that there was no need for one. They then blew the referendum, and let patent absurdities be claimed by some on the No side without correcting them, from blatant misrepresentations of articles to complete fictions. As a result they are stuck between a rock and a hard place. There will be no renegotiation - for that to happen would require the agreement of the other signatories and from day 1 the other signatories, most of whom have already ratified it, have made it clear there is no chance whatsoever of renegotiation. That is not, and never has been, on the table. So it boils down to either Lisbon or Nice. The trouble with Nice is that it is a legal dog's dinner of a treaty, widely viewed as the worst treaty ever drafted in the EEC/EC/EU's history, riddled with holes and conflicts - for example, it makes a reduction in the commission mandatory, but requires unanimity to work out how the number of the reduction is decided post the treaty's adoption, producing a danger that if the 'how' could not be agreed, legally a new commission could not be formed, and if no commission is formed, under co-decision the EU effectively stops working because it is like an engine where a range of bits must work together and if one bit breaks down the engine seizes up. So for example, if a new commission cannot be appointed, all the money that comes to Ireland and everywhere else stops, as legally if there is no commission there is no body to authorise it's issuing. The safety nets the Nice Treaty should have contained in case the new commission's size could not be agreed, and in a whole range of other areas, were not provided. Nice is effectively a high wire act without a safety net, with its workings based on a lot of keeping fingers crossed, because if something goes wrong . . . "oh * siúcra *".
The government is the author of the mess. They decided to go down an unnecessary route. They then ran a dog's dinner of a campaign and true to form tried to blame the opposition parties, even though it was
their own treaty, negotiated by them, in a campaign chosen by then, a date chosen by them, etc. It is up to them to decide what to do next, whether they want to try another referendum on another constitutional amendment, whether they want legally to revisit Crotty, whether they want to use Article 26 or whether they want to try parliamentary ratification. I doubt if any of the opposition parties will make whatever they try easy. They arrogantly brushed aside opposition concerns during the referendum. They two main opposition publicly pleaded with the government to announce the date and begin an early campaign, only to find Ahern and Cowen (to be fair to him, Dick Roche was also trying to push them into taking decisions, but his bosses were dragging their heals) wouldn't make up their minds. The Government created the mess, stuck with a treaty Europe insists it needs, to replace a messed up previous treaty, and public opposition. It is their responsibility to come up with a solution, one which somehow takes into account the vote in Ireland, and the decisions in 26 other countries. It isn't going to be easy, but that is their problem.