The Supreme Court has dismissed an appeal by the State against orders directing the release of three dissident republicans serving sentences in Portlaoise Prison.

The three men from Co Louth were convicted in England 14 years ago of trying to buy weapons and explosives on behalf of the Real IRA. 

They were jailed for 28 years.

The High Court ordered the release of Fintan O'Farrell and Declan Rafferty from Carlingford, and Michael McDonald from Dundalk in 2014. 

The State had wanted them to be detained until October this year.

High Court judge Mr Justice Gerard Hogan had found the court had no jurisdiction to retrospectively adapt the defective warrants under which the three men were detained in Ireland following their transfer from English prisons in 2006, so as to achieve compatibility with Irish law.

That decision was upheld by the Supreme Court by a majority of four to three.

The appeal against it was rejected by Mr Justice Liam McKechnie, Mr Justice John McMenamin, Ms Justice Mary Laffoy and Ms Justice Iseult O'Malley.

Chief Justice Susan Denham and Mr Justice Frank Clarke and Mr Justice Donal O'Donnell were in the minority.

In his ruling Mr Justice McMenamin said this was a troubling case and many would say the three should be made serve the full period of the sentence imposed.

But he said the process by which they were placed in detention in Ireland was fundamentally defective and the warrants were void from the beginning.