A High Court ruling on a challenge by Sinn Féin's Pearse Doherty to the Referendum Commission will be handed down this morning, just one day before the vote.
Mr Justice Hogan said that, given the importance of the issue, he would rule at 10.30am today.
The Donegal TD wants clarification on comments by the Commission's chairperson earlier this month in relation to Ireland's veto of the ESM.
Pearse Doherty's lawyers say they want a declaration to dispel the confusion as to whether the Government can still veto the ESM after the Fiscal Treaty is signed.
The spat related to an explanation given by chair of the commission, Mr Justice Kevin Feeney, early in the campaign.
Mr Doherty said this explanation had implied that Ireland could not reject the establishment of the new European €500bn bailout fund, the European Stability Mechanism.
They say the Referendum Commission has issued contradictory statements on the issue, but that some statements had received more publicity than others, inadvertently benefitting the Yes campaign.
When lawyers for the Referendum Commission countered that there had been no inconsistency, Pearse Doherty's lawyers replied that, in that case, they had got it wrong.
In its submissions, the commission denied there was any legal authority for the proposition that the Government had an executive power to veto the ESM having signed up to the agreement.
They reject out of hand that any statement by the Commission had favoured the yes side.
The outcome of the hastily arranged case will have no effect on the holding of tomorrow’s referendum, but will judge whether the commission made comments that were biased against the no side.
The commission had opposed Mr Doherty’s application. Michael Collins SC, for the commission, told the court the application was "flawed and misconceived".
Mr Doherty’s application focused on comments made by Mr Justice Feeney on May 3 when he said Ireland had "already agreed to the establishment of the ESM".
The statement added: "The Dáil and Seanad had yet to rectify the treaty" and "it was clear that a veto could have been exercised but Ireland has already agreed to the establishment of the ESM".
In an affidavit, Mr Doherty says he is not challenging the holding of the referendum or favouring any side, but rather is concerned with the conduct of the commission in relation to the comments made earlier this month.