Jack Whomes, 59, was given three life sentences and ordered to serve a minimum of 22 years in jail in 1998.
He and his friend Michael Steele, now 76, were found guilty at trial of shooting Tony Tucker, 38, Pat Tate, 37 and Craig Rolfe, 26, whose bodies were found in a Range Rover on a farm track in Rettendon, Essex, in 1995.
Whomes has been cleared for release following a Parole Board hearing earlier this month where he gave evidence via video link.
A summary of the decision said: “After considering the circumstances of his offending, the progress made while in custody and the evidence presented at the hearing, the panel was satisfied that Mr Whomes was suitable for release.”
He will have to follow strict licence conditions banning him from entering certain areas or contacting relatives of the victims.
Whomes must also provide details of his vehicle use and report for meetings with his probation officer.
The summary states: “The panel heard that Mr Whomes maintains that he did not commit the Index Offences and as a result little or no work had been completed to address offending behaviour.
“Mr Whomes had completed work to explore victim empathy and had developed his education and employment skills.
“Since being in an open prison, there had been no concerns reported about his behaviour, which the panel was told had been exemplary.”
Whomes has been granted temporary release over the last few years and witnesses recommended that he should be let out on life licence, the panel heard.
They also heard victim impact statements from relatives of the three murdered villains.
Doubts remain on the safety of the convictions and both men still deny involvement in the executions, which became known as the “Essex Boys” murders after a 2000 film of the same name starring Sean Bean.
Steele and Whomes were convicted on evidence from convicted fraudster Darren Nicholls, who claimed to have been their getaway driver.
Detectives spent 30 hours questioning Nicholls, and Steele and Whomes’ lawyers claimed he had fabricated the story.
London villain Billy Jasper had already admitted being the real driver, telling police he was paid £5,000 to take a hitman to the murder scene. Jasper was never charged.