The government has vowed to fight the decision to allow Shamima Begum, who left London as a schoolgirl to join Islamic State in 2015, back into the UK.
The family of Begum, 20, said they were heartened by the decision on Thursday letting her return to the UK to challenge the Home Office’s move to revoke her British citizenship.
Speaking via Tasnime Akunjee, a lawyer, the family said: “We understand there is still a long road ahead.”
The court of appeal partially overturned an earlier ruling by the Special Immigration Appeals Commission (Siac) this year, a tribunal which held that she had not been illegally rendered stateless while she was in Syria because she was entitled to Bangladeshi citizenship.
Concluding, Lord Justice Flaux said: “Notwithstanding the national security concerns about Ms Begum, I have reached the firm conclusion that given that the only way in which she can have a fair and effective appeal is to be permitted to come into the United Kingdom to pursue her appeal … the LTE [leave to enter] appeals should be allowed.”
The judge added: “Fairness and justice must, on the facts of this case, outweigh the national security concerns.”
The court of appeal also said Siac had failed to consider the evidence properly when it had made its initial decision to revoke Begum’s citizenship, because it had not assessed the “risk of transfer to Iraq and Bangladesh and mistreatment there”. The courts have heard that if Begum were forced to go to Bangladesh she could be hanged.
Flaux and the two other judges on the court, in a unanimous ruling, concluded that Siac, which specialises in complex nationality cases, should therefore hear the citizenship case again.
The government said it would appeal against the decision and apply for the court’s judgment to not be implemented until then.
A Home Office spokesperson said: “This is a very disappointing decision by the court. We will now apply for permission to appeal this judgment, and to stay its effects pending any onward appeal.”
But it is not clear how easy it would be in practice for Begum to return from Syria, and the court of appeal acknowledged she “could be arrested and charged” upon her arrival in the UK and held in custody to await trial.
Whitehall sources also warned that anybody helping her return could also be at risk of a criminal offence, although Siac itself had also conceded that her conditions in the camp where she lived now were so bad it amounted to “inhuman or degrading treatment”.
The human rights group Liberty, which intervened in the case, said that Begum’s right to a fair trial had been upheld. Katie Lines, a lawyer with the group, added: “Banishing someone is the act of a government shirking its responsibilities and it’s critical that cruel and irresponsible decisions can be properly challenged and overturned.”
Begum left Bethnal Green, east London, with two teenage friends in 2015 to join Isis, when the terror group was at its height. Four years later, after its territorial defeat, she was found in a Syrian refugee camp, nine months’ pregnant.
Sajid Javid, the home secretary at the time, stripped her of her British citizenship later that month, arguing she had the right to become a Bangladeshi citizen, the birth country of her parents. Begum has never visited Bangladesh.
Ministers have been increasingly using a power to remove people’s British citizenship if they can argue that doing so is for “the public good” and they believe the target can obtain citizenship in another country.
The power has been applied to more than 150 people since 2010, prompting arguments that it effectively creates a two-tier form of citizenship, with a lesser form applying to people with ancestry overseas.
Javid’s action prompted a high-profile legal battle in which Begum’s lawyers also argued she could not properly defend herself because she remained in a camp in north-east Syria unable to properly contact her lawyers.
Begum’s child Jarrah died shortly after Javid’s decision was announced. She has said she had two other children while living under Isis, but that they too died. In February she was pictured living in a heated tent in the al-Roj camp in Syria.
British security sources argue that Begum represents a security risk, and that she was a member of al-Hisba, Isis’s morality police, during which time she carried a Kalashnikov rifle and had a reputation for strictness. Begum also allegedly “stitched suicide bombers into explosive vests”.
Begum’s lawyer, Daniel Furner, of Birnberg Peirce solicitors, said the ruling would allow the young woman to “give her side of the story”. He added: “The court itself noted the ‘obvious’ difference between interviews given to journalists, and instructions provided to a solicitor in court proceedings.
“Ms Begum is not afraid of facing British justice, she welcomes it. But the stripping of her citizenship without a chance to clear her name is not justice, it is the opposite.”