The Supreme Court has refused to permit five TDs to be joined to businessman David Hall's challenge to the Government's payment of promissory notes in favour of the former Anglo Irish Bank and other financial institutions.
Today's ruling does not prevent Clare Daly, Luke Flanagan, Mick Wallace, Joan Collins and Catherine Murphy from bringing their own challenge in the High Court to the payments.
The TDs wanted to be joined to Mr Hall's Supreme Court appeal after the High Court's recent decision.
The High Court ruled that because he is not a TD, Mr Hall does not have the required legal standing to challenge the lawfulness of the promissory notes.
The court heard today that a €25m payment to EBS is due in June.
The three-judge Supreme Court said there was no basis for the TDs to be joined to the appeal.
In his ruling, Mr Justice Nial Fennelly said it was not disputed the five TDs have an "honest and genuine" interest in the key issue at the heart of the litigation, whether the promissory note payments were made lawfully.
The TDs' application was essentially very simple, he said.
Mr Hall had failed in the High Court because he was not a TD, while the five applicants are TDs and their being joined to the case could solve the problem of Mr Hall's legal standing.
Another equally simple answer was that the TDs could have sought to join the case in the High Court, but they had not applied to do so, he said.
The TDs wanted to join the appeal so as to support Mr Hall's argument he has the necessary legal standing to bring the case, the judge said.
Mr Hall himself could make that case, it involved an issue of law, and the addition of the TDs as appellants would add nothing to the strength of the legal arguments.
While the TDs, as members of the Dáil, had the necessary legal standing to challenge the promissory note payments of their own accord, their addition as appellants would add nothing to Mr Hall's arguments in the appeal.
They had no special standing to protect the public interest, he added.
The judge also noted, if Mr Hall wins his appeal against his lack of standing, the case will return to the High Court to have the substantial issues addressed about the legality of the payments.
At that stage, the High Court could join the TDs to the case if it decided they were necessary.
If Mr Hall lost his appeal, and the TDs had been joined as appellants, they would effectively have been joined as a substitute for Mr Hall, the judge noted.
Such a situation raised not just procedural, but fundamental difficulties.
The judge said to allow the TDs substitute themselves for the original, but unsuccessful, appellant in an appeal so as to continue the case in the High Court to which they were previously not parties would be unprecedented.
In all the circumstances, he was satisfied the TDs' application did not come within the purpose of the relevant court rules and should be refused.
Mr Justice Liam McKechnie was in agreement and said there was no doubt the TDs themselves have the power to litigate the issues in the case and could bring their own action.
A rejection of this application to be joined would not deny them their right to justice.
In his view, the TDs would never have intervened but for the precariousness of Mr Hall's standing. It seemed to him if Mr Hall won his appeal on standing, the TDs should withdraw from his action.
He said the position of Mr Hall and the TDs would not be favourably adjusted by the TDs being joined to the case.
Mr Justice John MacMenamin also agreed the TDs should not be joined.
Mr Hall's main claim is that under the Constitution the Dáil must authorise the State's financial expenditure, but it had never voted in favour of the promissory notes, under which €31bn has so far been paid, with more payments to come.
The State has accepted there was no Dáil vote, but denies the specific mandate of the Dáil was required.
It claims the notes could be lawfully issued under the provisions of the Credit Institutions (Financial Support) Act 2008 and/or the Anglo Irish Bank Corporation Act 2009.
Mr Justice Fennelly previously remarked, while it was for the Chief Justice to decide whether to grant priority for any appeal, the Supreme Court has so far granted priority to some 71 appeals and was not granting any further priority hearing dates this court term except in exceptional circumstances.