Abu Bakar Bashir is expected to be allowed out of jail to attend court next week, where another violent cleric is ready to support his bid for freedom.
Bashir, founder of Jemaah Islamiah, is applying for a judicial review in the hope he will be released from his 15-year sentence.
South Jakarta District Court spokesman Made Sutrisna told AAP a panel led by chief judge Achmad Rivai will examine the application next Tuesday.
The judges will also consider moving any future hearings to Cilacap, the port town closest to Nusakambangan island where the 77-year-old is jailed.
Bashir spent 26 months in jail over the Bali bombings that killed 202 people - including 88 Australians - before being acquitted.
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He is now serving time for helping set up a terrorist training camp in Aceh.
If the judicial review of that case is granted, lawyers for Bashir plan to bring three witnesses with previously unheard evidence.
It's understood one of them will be Muhammad Rizieq Shihab, founder of the hardline Islamic Defenders Front, or FPI.
The FPI is notorious for violent clashes in Indonesia, raiding bars that open during Ramadan, and last year threatening Jakarta's Christian governor, Basuki Ahok Tjahaja Purnama.
In 2012 the group forced the cancellation of Lady Gaga's Jakarta concert by threatening violence if it went ahead.
Family members of Bali bombing victims are shocked at Bashir's bold bid, given evidence that only last year he was supportive of ISIS.
Bashir was photographed pledging his allegiance to the group before an audience at his prison.
However his lawyer Mahendradatta has told AAP that Bashir has since learned more about ISIS, and now "is not supporting anything".
