The five-judge Supreme Court turned down an appeal by Michael O'Neill and John Quinn both of whom are detained in Castlerea Prison against the High Court's refusal of their application for early release under the Good Friday Agreement.
Sinn Féin's Martin Ferris described the decision as profoundly disappointing and in contradiction of the Good Friday Agreement.
O'Neill, an unemployed general operative, is serving a total of 11 years for the manslaughter of Det McCabe, the malicious wounding of Det Garda Ben O'Sullivan at Adare on June 7, 1996 and for possession of firearms. Quinn is serving a six-year sentence for conspiracy to commit a robbery at Adare in June 1996.
Proceedings by two other men jailed for the manslaughter of Det McCabe, in which they are seeking their release under the Agreement, stand adjourned before the High Court pending the Supreme Court decision in the appeal by O'Neill and Quinn.
Pearse McAuley, originally from Strabane, Co Tyrone, and Jeremiah Sheehy, from Limerick, are serving 14 and 12-year terms, respectively. In January 2002, they initiated proceedings for their release under the terms of the Good Friday Agreement.
Some 57 prisoners here and 444 in Northern Ireland have been released to date under the Agreement. Last March, the High Court rejected the application by O'Neill and Quinn for their release. It found there was no obligation on the minister for justice to consider the men's application to specify them as qualifying prisoners or to seek the advice of the Release of Prisoners' Commission on their release. In the unanimous judgment of the Supreme Court, the chief justice said the Government, as had been made clear by the minister in statements in the Dáil, that the release of prisoners' provisions of the Good Friday Agreement would not be operated in the case of persons convicted in connection with Det McCabe's killing.
While it was conceded that other prisoners who had been convicted of equally or even more serious crimes, including the murder of gardaí, it was not suggested that any of the persons released were in the same position as the applicants. O'Neill and Quinn at the time of the British-Irish and Good Friday Agreements had been charged with the killing of Det McCabe but whose trial had yet to take place.
The court ruled that if they were to be treated as persons entitled to the benefit of those provisions, their trial would have taken place in circumstances where, irrespective of any verdict reached, the entire of any sentence imposed on them would have been remitted. The minister had made it unambiguously clear that the Government did not regard that as acceptable.
Mr Ferris said the Good Friday Agreement does not draw any distinction between prisoners belonging to organisations on cessation at the time of its signing.
"Today's judgment confirms that these men are in fact qualifying prisoners under the terms of the Good Friday Agreement as it has been applied to others convicted of equally or even more serious offences.
"However, in its ruling, the court has unfortunately said that it is acceptable for one party to the Good Friday Agreement to act unilaterally and take on itself to go outside the terms of that agreement.
"That is completely unacceptable and undermines the agreement itself," he said.