The Irish Republican Army, which has expelled three members over the killing, said in a statement on Tuesday it had met the sisters and fiancee of Robert McCartney and offered its own form of justice but the family wanted the killers dealt with by the courts.
"The IRA representatives detailed the outcome of the internal disciplinary proceedings thus far and stated in clear terms that the IRA was prepared to shoot the people directly involved in the killing of Robert McCartney," it said.
"The family made it clear that they did not want physical action against those involved."
The statement, signed "P O'Neill", the name traditionally used in IRA communiques, did not spell out whether it had intended to kill those responsible or carry out a non-lethal punishment shooting known in Northern Ireland as "knee-capping".
Beaten and stabbed
McCartney, a 33-year-old forklift truck driver, was beaten and stabbed to death in a bar at the end of January by a gang that included a number of IRA men.
His family has accused the IRA of cleaning the bar of evidence and intimidating witnesses.
"The IRA representatives detailed the outcome of the internal disciplinary proceedings thus far and stated in clear terms that the IRA was prepared to shoot the people directly involved in the killing of Robert McCartney"
Irish Republican Army
Britain's Northern Ireland Secretary Paul Murphy said he was appalled by the IRA's latest intervention.
"Any sort of punishment ought to come through the courts, through due process of the law," he said. "There is no place for arbitrary justice, there is no place for kangaroo courts or capital punishment in this country."
The outspoken campaign waged by the McCartney family is remarkable because they come from a working-class Catholic neighbourhood in Belfast where people distrust the mainly Protestant police and the IRA has regarded itself as the law.
McCartney's killing heaped pressure on the IRA and political ally Sinn Fein, coming weeks after the armed group - which called a ceasefire in its campaign against British rule in 1997 - was blamed for a $50 million bank raid.
"This obscene proposal by the IRA to kill the alleged murderers of Robert McCartney is sinking to the lowest depths of terror in the community," said Eddie McGrady, a legislator from the moderate Social Democratic and Labour Party, Sinn Fein's main competitor for Catholic votes.
Ian Paisley, leader of the hardline Protestant Democratic Unionist Party, said it "confirms again that terrorism is the only stock in trade of Sinn Fein/IRA".
Northern Ireland's 1998 Good Friday peace deal largely drew a line under the three decades of violence in the province that claimed some 3600 lives.
But crime, in the form of punishment beatings, stabbings and robberies, persists.