Brian Rattigan has lost his appeal against a murder conviction on the grounds that a new law on witness statements was unfairly applied retrospectively at his trial.
The 31-year-old from Cooley Road in Drimnagh was found guilty by a jury of stabbing Declan Gavin to death outside Abrakebabra in Crumlin on 25 August 2001.
It was the first of more than 16 murders in the past 12 years arising out of a feud between Rattigan's criminal gang and a rival drug dealing gang in Dublin.
He is also due to be sentenced in a separate case next month after he was convicted of dealing drugs from his cell in Portlaoise Prison.
Rattigan stabbed Mr Gavin in a feud that followed the seizure of heroin and cocaine in a Dublin hotel room in 2000.
Mr Gavin was in the hotel room, but got away, while two others were caught and jailed.
He was then wrongly labelled a garda informer, which started the feud.
Rattigan was eventually convicted in December 2009 of the murder of Mr Gavin after two murder trials and the intimidation of jurors and witnesses.
The Court of Criminal Appeal also found that Rattigan was not unfairly treated by gardaí when he was arrested, detained and questioned, by the evidence used against him or by the judge during his trial for murder.