Irish soldiers' representative group, Pdforra, has attacked the decision of Irish Justice Minister Brian Lenihan to approve the transfer of former private and triple murderer Michael McAleavey to a jail in Northern Ireland.
The group said it was surprised and disappointed at the decision.
General secretary Gerry Rooney said: "We believe and have always believed that Mr McAleavey should serve his full sentence in this State.
"His crimes relate to this jurisdiction and the many people so seriously affected by his crime live here.
"This announcement has been made on the eve of the 25th anniversary of the murders of three of his army colleagues and is particularly insensitive to the families involved," Mr Rooney added.
He called on the minister to reconsider his "surprising" decision.
Pdforra has been to the forefront of a long running campaign to ensure that McAleavey was not transferred across the Border.
McAleavey had applied to be moved from Mountjoy jail in Dublin to Maghaberry prison, near Lisburn, Co Antrim, to be closer to his family. He is from west Belfast.
The move has been on the cards since the end of last year when the then Northern Ireland prisons minister Paul Goggins offered no objections to a transfer.
McAleavey received a life sentence for the October 1982 killings in Lebanon, where the soldiers were on UN peacekeeping duty. He was 21 at the time.
He opened fire on fellow privates Peter Burke and Thomas Murphy and Corporal Gary Morrow, from Lurgan, at Tibnin Bridge, South Lebanon, on 27 October 1982. He fired 33 shots, 18 of which hit the soldiers.
The west Belfast man initially said his unit had been attacked by a Lebanese pro-Israeli Christian militia but later admitted that he "cracked" under a combination of pressure and heat exhaustion.
McAleavey has already served 24 years behind bars and is the ninth longest serving prisoner in the State, having been convicted of the murders in September 1983 after a lengthy court martial at the Curragh military camp.
His solicitor, Joe Rice said yesterday he did not know yet when the transfer would take place.
"This is the end of a long and difficult process," he added. "The decision was taken on humanitarian and compassionate grounds. It has come as a great relief to him and his family, especially his father James (77), who, for health reasons, has been unable to visit his son for 13 years."
After the transfer, a decision on his release will become an issue for the Northern Ireland Life Sentence Review Commission.
During a previous application, Mr Rice had argued that if his client had joined the IRA and killed three British soldiers, he would have been released under the terms of the Good Friday agreement.
McAleavey was jailed for shooting his colleagues, Corporal Gregory Morrow (19), Private Thomas Murphy (19) and Private Peter Burke (20), on October 27, 1982, at an Army post at Tibnin bridge, in south Lebanon.
His application to be moved was made under the Republic's Transfer of Sentenced Persons Act 1995, which allows prisoners to be transferred if there was agreement from the authorities in the two relevant jurisdictions.
Other long serving "lifers" in the Republic include double murderer Malcolm Macarthur, admitted in January 1983, and the English killers, John Shaw and Geoffrey Evans, who were convicted in 1978.
However, top of the list of long termers is Jimmy Ennis, who was sent to jail for murder in 1964. Ennis is now in his mid-70s and is not anxious to leave the "open" prison at Shelton Abbey, outside Arklow.