Anyone convicted of involvement in Det Garda Jerry McCabe's murder will not qualify for early release under the terms of the Belfast Agreement, the Taoiseach has said.
At Adare yesterday, near the scene of the 1996 shooting in which the detective died, Mr Ahern said the Belfast Agreement, as it related to the release of prisoners convicted of killing gardai, would have to be honoured.
But he added that the agreement did not cover anyone who might be convicted of involvement in the killing of Det Garda McCabe and seriously injuring a colleague because at the time the agreement was signed nobody had been charged with this offence.
Mr Ahern was playing host to the Speaker of the United States House of Representatives, Mr Newt Gingrich, who has been leading a congressional delegation in Ireland for the past week. He travelled by helicopter from west Kerry, where he is on holiday, to meet the delegation at the Adare Manor Hotel.
Mr Ahern told journalists: "I signed an agreement in which some of the persons involved in activities against gardai will be released."
He said he knew it was hard on the families of those involved, but the influence of the prisoners from inside had formed a central part of the ceasefire.
Mr Gingrich said, "as a former history teacher", he believed there was now "a rare historical moment in Ireland over the next six months when every political leader in Northern Ireland will have to decide each morning whether they want to posture or to progress the peace process".
In his formal address to the delegation, the Taoiseach paid tribute to two groups in the US Congress, the Friends of Ireland and the Ad-Hoc Committee on Irish Affairs.
Last night the delegation members attended a dinner as guests of Shannon Development at Knappogue Castle. They will fly home from Shannon today.
Mr Alan Dukes of Fine Gael said yesterday that people convicted of the murder of gardai should be released as provided for under the Belfast Agreement, despite the difficulty members of the force and others had with the idea.
At the McGill Summer School in Glenties, Co Donegal, Mr Dukes said he shared the difficulty the Garda had in accepting this conclusion, but he believed the same treatment should apply to prisoners north and south of the Border.
"It is valid to ask whether a person convicted of killing a member of the RUC, a force which operates in a higher risk environment than the Garda, should be treated less severely than a person convicted of killing a garda," he said. Mr Dukes's comments were about prisoners in general who were convicted of killing gardai, and did not refer to the case of anyone who might be convicted in the future in relation to killing Det Garda McCabe.