Australian authorities have revoked the citizenship of 27-year-old Neil Prakash over his association with the terrorist group.
Home Affairs Minister Peter Dutton is insisting Melbourne-born Prakash has dual citizenship with Fiji, and are trying to send him there, but Fiji says Prakash is an Australian.
Australia correspondent Murray Olds told Tim Dower everyone is trying to wash their hands of him.
But that is news to Fiji Prime Minister Frank Bainimarama, who says the country has no records of him ever being a citizen.
International law says countries cannot leave somebody stateless, which is complicating the issue even further.
LISTEN ABOVE AS MURRAY OLDS SPEAKS TO TIM DOWER