Shamima Begum, who left the UK for Syria to join the Islamic State group as a teenager, will not be allowed to return and fight her citizenship case, the Supreme Court has ruled.
The court said in a unanimous ruling that her rights were not breached when she was refused permission to return.
Ms Begum, 21, wants to come back to challenge the home secretary's decision to remove her British nationality.
She is in a camp controlled by armed guards in northern Syria.
Ms Begum was 15 when she and two other east London schoolgirls left the UK in February 2015 and travelled to Syria to join the Islamic State group.
In 2019, the then-Home Secretary Sajid Javid stripped Ms Begum of her citizenship on national security grounds.
Last July, the Court of Appeal ruled that the only fair way forward was to allow her into the UK because she could not effectively appeal against the decision from the camp in northern Syria.
The Home Office subsequently appealed to the Supreme Court to reconsider the Court of Appeal's judgement, arguing that allowing her to return to the UK "would create significant national security risks".
On Friday, Lord Reed, president of the Supreme Court, said the government had been entitled to prevent Ms Begum from returning to the UK.