Businessman Denis O'Brien initiated legal proceedings against the Dáil's Committee on Procedures and Privileges in August 2015.
Mr O'Brien took issue with the CPP's decision not to sanction Social Democrats TD Catherine Murphy and Sinn Féin TD Pearse Doherty for making allegations against him under Dáil privilege.
Ms Murphy and Mr Doherty had made a number of claims in May and June 2015 about the sale by the Irish Banking Resolution Corporation of Siteserv, a company owned by Mr O'Brien.
The businessman made an initial complaint to the CPP urging disciplinary action be taken.
He argued the speeches made were a breach of his rights under the Constitution and European Convention on Human Rights.
After taking legal advice from the Oireachtas legal counsel, the CPP rejected assertions by Mr O'Brien that Ms Murphy or Mr Doherty had abused Dáil privilege.
It said it could not determine if the allegations were true or false until the Commission of Investigation into certain Irish Bank Resolution Corporation transactions was complete.
The CPP ruled their comments were not an abuse of the deputies’ position and no further action was taken.
Mr O’Brien wrote to the committee in August 2015 confirming he would be suing each individual member of the committee.
This included former ceann comhairle Sean Barrett and current Minister of State Paul Kehoe.
Mr O’Brien said he was seeking a declaration that the TDs on the committee are guilty of an “unwarranted interference with the operation of the courts and have caused or permitted a breach” of his constitutional rights.
The businessman said article 40.31.1 of the Constitution guaranteed to respect, defend and vindicate the personal rights of the citizen.
Mr O'Brien's solicitors, William Fry, said this had not been not upheld by the Dáil committee.
A High Court case was initiated in late 2016 and Mr O'Brien was the sole witness.
In his evidence, he alleged Ms Murphy and Mr Doherty “clearly disregarded” the constitutional separation of powers between parliament and the courts when they made statements in the Dáil about his banking affairs.
Mr O'Brien had been pursuing a High Court injunction against RTÉ preventing it from broadcasting a report about his personal banking arrangements with the IRBC.
He said by allowing TDs to make the utterances in the Dáil chamber, the committee had failed to enforce the sub-judice rule and so had interfered with the courts’ role.
The businessman said the CPP failed to “properly police” deputies Murphy and Doherty.
Senior counsel for the committee Michael Collins had told the court there would be "appalling consequences" if the courts sought to examine or restrain statements made in the Dáil.
Members of the committee and the two TDs have been prevented from making public statements on the case.
