The court of appeal’s decision due on Friday on whether Shamima Begum, who travelled to Syria to join Islamic State as a child, was unlawfully stripped of her UK citizenship is the latest step in a long-running battle she has fought against the government. Here is the history of the case and why it has attracted so much publicity. Who is Shamima Begum and what did she do? Begum was born in England to parents of Bangladeshi heritage. In 2015, aged 15, she left her home in east London with two school friends, prompting an international police hunt, to travel to Islamic State (IS) territory in Syria. Shortly after she arrived in Syria, Begum married a Dutch national, Yago Riedijk. When IS was defeated by a coalition involving the UK and US, hundreds of women and children, including Begum, were picked up by Syrian Kurdish ground forces and detained in refugee camps. She was found in al-Hawl refugee camp in north-east Syria in 2019 by a Times journalist, whom she told that she hoped to return to the UK but did not regret her decision to join IS. Why was she stripped of her British citizenship? Amid widespread media outrage about Begum’s lack of contrition, the home secretary at the time, Sajid Javid, used his powers to revoke citizenship if “that deprivation is conducive to the public good”. He told MPs that those who travelled to IS “all supported a terrorist organisation and in doing so they have shown they hate our country and the values we stand for”. UK legislation does not allow deprivation of citizenship if someone is rendered stateless but Javid told Begum’s family that as her parents were of Bangladeshi heritage, she could apply for citizenship of that country. Begum said she had never visited Bangladesh, and the Bangladeshi foreign minister said she would face the death penalty if she went there. She remains in a Kurdish-administered refugee camp in north-east Syria while her lawyers have fought a series of court battles since the revocation of citizenship. What was the basis of the latest legal challenge? Begum’s lawyers told the court of appeal that Javid’s decision was unlawful because he failed to consider whether she had been groomed and trafficked, and so breached anti-slavery protections in British law. Similarly, they said a decision by the special immigration appeals commission (Siac) last year to uphold Javid’s ruling was unlawful. The Siac judges said there was “credible suspicion” that Begum had been trafficked for sexual exploitation, they were concerned by Javid’s “apparent downplaying of the significance of radicalisation and grooming” and that “political rather than national security factors drove the outcome”. But ultimately they said the decision was Javid’s to take, weighing up the competing factors including national security. This conclusion was echoed by the arguments at the court of appeal. What are the prospects of Begum being able to return to the UK? There is no prospect of Begum being able to return to the UK in the short-term. Even if the court of appeal decided in her favour, given the high-profile nature of the case and the political considerations, it is inevitable that the government would appeal. Even if it did appeal, there are several British women detained in north-east Syria who retain British citizenship but have not been repatriated What are the wider ramifications of the case? The UK has been criticised for not repatriating its nationals from north-east Syria – it has brought back just two adults to date – putting it out of step with allies including Canada, Australia and some European countries. It is also the only country along with Bahrain to frequently revoke citizenship. There are an estimated 20-25 women or families with British nationality still held in Syrian camps, plus others, such as Begum, whose citizenship was removed and are challenging the decision in the UK courts.