Businessman Denis O'Brien has lost his High Court action over statements made in the Dáil about his banking affairs.
Mr O'Brien asked the court to reprimand TDs Catherine Murphy and Pearse Doherty over their statements, which he said interfered with a court case he was taking against RTÉ.
But the court ruled the Constitution does not permit it to intervene in relation to utterances made in the Dáil.
Mr O'Brien claimed the TDs clearly disregarded the separation of powers, when they revealed information in the Dáil about his banking affairs in 2015.
He claimed they disclosed confidential matters that he had gone to court to stop RTÉ broadcasting.
In her judgment, Ms Justice Úna Ní Raifeartaigh said the release of confidential information which is the subject of a court order creates a very particular problem at the intersection between parliamentary speech and the administration of justice.
She said the tension between the freedom of speech in the Dáil and the role of the courts reaches an extremely acute point in a case where a member of the Houses of the Oireachtas releases confidential information, subject to a court injunction, into the public arena by means of an utterance in the House.
But she said if the court were to grant the reliefs sought by Mr O'Brien, it would be reaching a formal legal conclusion as to the content, effect and motivation of the speakers and would be a judicial condemnation of what had been said by two Dáil deputies.
She said this was forbidden by the Constitution.
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The judge also said if she made the declarations sought by Mr O'Brien it might have a chilling effect on speech more generally.
She said the Constitution did not allow a court to draw dividing lines between "legitimate" and "illegitimate" speech in the Oireachtas.
She said it would be very far reaching indeed if Dáil deputies could not speak about a matter, merely because court proceedings had begun.
The judge ruled there was no jurisdiction for the court to intervene in an exceptional case relating to Dáil statements.
And, she said, even if there was, she did not believe what was said in this case would fall into an "exceptional" category.
She said she took this view with her "eyes wide open" to the fact that the utterances made Mr O'Brien's court case against RTÉ essentially pointless, damage was undoubtedly done to him and the release of the information appeared to have been done in a deliberate and considered manner by the deputies in question.
But she said an exceptional category of utterances would seem to require some grave threat to the democratic order.
Ms Justice Ní Raifeartaigh also ruled that under the Constitution she did not have the power to rule on the issues raised by Mr O'Brien in relation to the Dáil Committee on Procedure and Privileges and how it dealt with the statements and his complaint in relation to the statements.
She said the framers of the Constitution made certain choices - and one of those was to create a strong set of privileges and immunities for parliamentary speech.
She said the language used to describe them, signalled the importance with which freedom of speech in the Oireachtas and therefore in the Irish democratic State was viewed. She ruled that she did not have the power to rule on any of the issues raised by Mr O'Brien.
Ms Justice Ní Raifeartaigh said there was no doubt that the impact of parliamentary speech could potentially be damaging and dangerous to the individuals who were the subject of such utterances.
But she said under the Constitution, the courts did not have a role in policing parliamentary utterances, except in some kind of extremely exceptional and limited circumstance of which Mr O'Brien's case was not one.
However, she said she had received submissions outlining reports from the UK and New Zealand where there was discussion of these problems as well as potential solutions by way of reforming parliamentary procedures.
She said it may be that this case threw a light on the need for a general examination of this area by a parliamentary committee, which would take into account issues such as whether and when a Dáil deputy may discuss matters before the courts, and reveal matters subject to an injunction.
She said it might not be inappropriate to say there seemed to at least some ambiguity and lack of clarity as to current procedures and parameters concerning speech potentially affecting matters before the court.
She said, however, any discussion of this could progress in the public arena and in the Houses of the Oireachtas, but not before the court.
If a signal was to be sent out to prevent future revelations in the Dáil of private information subject to an injunction, it must come from the court of public opinion and the houses of the Oireachtas but not from the courts of justice.
Speaking outside the court Ms Murphy said she was pleased with the court's ruling, which she said could hardly have gone any other way.
The Social Democrat TD said she had only every acted in the public interest.
Ceann Comhairle Seán Ó'Fearghail also welcomed the judgment but said he would not be in a position to comment further until a detailed examination of it and its implications for the Oireachtas has been concluded.