Persona launched legal proceedings against the Government following the conclusion of the Moriarty Tribunal.
The Persona consortium, which is headed by businessman, Tony Boyle, had been one of the unsuccessful applicants for the second GSM phone licence in 1996.
Esat Digifone, which was controlled by Mr O’Brien, emerged victorious from the competition. The circumstances of the awarding of the licence became the subject of the long-running Moriarty Tribunal, which published its findings in 2011.
It concluded that the former minister for communications, Michael Lowry, had helped deliver the GSM licence for Mr O’Brien.
Mr O’Brien has consistently denied that there was any wrongdoing. He has said on a number of occasions that he was willing to defend the Esat mobile phone licence in a court of law.
Persona had take legal proceedings against the State only in its attempts to seek damages. Mr O’Brien had applied to join the State as a defendant.
In his judgement, Mr Justice Ryan concluded: “If Mr O’Brien is not joined as a defendant and is left to stand by as the plaintiffs’ claim is presented against the state defendants only, he and the court will be observing a drama unfold in which he is the central participant but without any entitlement to intervene.
“The case alleging misconduct of the most serious nature will proceed without any involvement of the person alleged to be the major wrongdoer.”
Businessman Declan Ganley and the telecoms group, Comcast, are also taking an action against the State and Mr O’Brien over the mobile phone licence.