The case of Syrian runaway Shamima Begum, who is fighting to return to the UK, will go to the Supreme Court.
The Court of Appeal decided that the case raised a point of law of public importance that only the Supreme Court can resolve.
Earlier this months, three Court of Appeal judges ruled Ms Begum should be allowed back to London to fight for the return of her citizenship.
The government said that decision was deeply flawed.
Ms Begum, now 20, was one of three schoolgirls who left London to join the Islamic State group in Syria in 2015.
After she was found in a refugee camp in 2019, her British citizenship was revoked by former Home Secretary Sajid Javid on security grounds.
Separately, the court has revealed that an investigation is under way in Whitehall as to how the Sun newspaper got hold of a copy of the previous judgement on 16 July.
Lady Justice King, the head of the panel of three judges, said they were referring the newspaper to the Attorney General because of a potential contempt of court in publishing a story about the judgement before it was announced in court.