The British-born Muslim convert known as "Jihadi Jack" is set to be repatriated from a prison camp in north-east Syria.
Jack Letts, 28, who had held dual British and Canadian citizenship, will be sent back to Canada along with 22 others from the camp.
He begged to be allowed to return to the UK, insisting he had "no intention" of killing Britons, but the government stripped his citizenship in 2019, making him the responsibility of the Canadian government.
The Oxfordshire man said he was an "enemy of Britain" after travelling in 2014 to Syria to allegedly fight with ISIS as a teenager.
In a ruling on Friday, the Canadian federal court said the government must bring home four Canadian men - after an agreement was reached earlier this week to repatriate six women and 13 children.
A court case was brought against the government by the detainees' relatives, who argued that preventing them from entering Canada would violate their constitutional rights.
Lawrence Greenspon, the lawyer for most of the individuals, said to the press: "These are Canadian citizens, they are being unlawfully, arbitrarily detained in either detention camps or in prisons, they haven't been charged with anything."
There are hundreds of foreign nationals who have been held in the camps ever since ISIS lost the ground war in Syria.
Repatriation efforts by western nations have been ongoing, however, Britain is far behind its counterparts.
It is estimated the UK has repatriated around 11 nationals (all but one of these are children), in comparison to 100 by Germany, close to 90 by France and over 200 by Tajikistan.
In an interview with Sky News, Mr Letts confessed to fighting against the Syrian regime but said he regretted being with the "wrong people".
Jack Letts's parents, Sally Lane and John Letts, said they were "overjoyed" at the news of his release from the camp.
Ms Lane told Middle East Eye: "Britain, in particular, which has been the most recalcitrant and authoritarian government over this issue, should take note of this judgement and bring all its people home."
The family have long stated that there is no evidence that he was an IS fighter and say he was imprisoned by IS and spent much of his time in Syria in hiding before escaping from territory controlled by the militant group in 2017.
