Umar Patek, who was jailed for 20 years over his role in the 2002 Bali bombings, has been given a five-month reduction as part of Indonesia's Independence Day celebrations.
Australian Prime Minister Anthony Albanese said that the decision would add to the distress and trauma of victims' loved ones coming up to the 20th anniversary of the attack that killed 202 people, 88 of whom were Australians.
Patek was accused of being the expert bomb-maker for Jemaah Islamiyah JI, a South-East Asian terror network linked to Al Qaeda.
Evidence in his 2012 trial showed that former Al Qaeda leader Osama bin Laden gave JI $30,000 to wage jihad and Patek might have met him in a Pakistani town, a claim Patek repeatedly denied.
After the bombings, he went into hiding, being on the most wanted terrorist list in several countries, with the US offering a $1 million bounty for his head.
In 2011, Patek was eventually captured in Abbottabad, Pakistan, and extradited to Indonesia.
On top of his convictions over the Bali bombings, he was found guilty of weapons and conspiracy charges over a terrorist training camp in Aceh in 2009, and for mixing explosives for a series of Christmas Eve attacks on churches in 2000.
Local media reports said Patek has been involved in a de-radicalisation program for several years.
In 2015, Major General Agus Surya Bakti, who led the Indonesia's de-radicalisation efforts through its anti-terrorism agency, spoke of Patek's success in the program.
He said it was an extraordinary thing.
On October 12th, 2002, about 11 pm, the bombs went off at the Sari Club and Paddy's Bar in Kuta.
Patek made some of the bombs used in the attack, with local media calling him Demolition Man during his trial.
He admitted to bringing 50 kilograms of the explosives into filing cabinets that were used to carry the bomb to the Sari Club.
During his trial, Patek downplayed his role in the terror plot and argued that he didn't know how the bombs would be used.
What do we know about his sentence?
He was spared the death penalty because he cooperated with investigators and apologised to the victims' families, eventually being sentenced to 20 years in prison.
He was granted routine remissions in his sentence, which has brought his release date forward to 2029.
With gradual reductions and good behavior, prisoners can get parole after serving about two thirds of their sentence.
He was due to be eligible for parole in January.
He could be released within a few days, but that is only if he is granted parole.
The ABC has been told that terrorists aren't usually eligible for parole.
Indonesian authorities say no decision has been made on whether he will be released.
If he's not granted parole, he'll be in prison until 2029.
On ABC Breakfast, Mr Albanese said that his government was in contact with Indonesia about this, but didn't go into specifics:
In 2008, Imam Samudra, Amrozi and Mukhlas were executed for their roles in the attack.
Abu Bakar Bashir - who was found guilty of conspiracy over the Bali bombings - was released from prison after 26 months in 2006 after his sentence was shortened.
He was given a 15-year jail sentence in 2011 for supporting militant training camps, but was released last year.
As former military commander of JI, Aris Sumarsono — better known as Zulkarnaen — was accused of masterminding the attacks.
He was sentenced to 15 years in prison on a string of terror charges in January, but was unable to be tried in relation to the Bali bombings because the statue of limitations had expired.