A woman who left the UK as a 15-year-old schoolgirl to join ISIS should be allowed to return to challenge the government’s decision to strip her of British citizenship, judges ruled on Thursday. Shamima Begum was one of three girls who travelled to Syria in February 2015, where she married an ISIS fighter and had three children, all of whom died. Ms Begum, now 20, was found in February last year in a Syrian refugee camp. The British home secretary at the time, Sajid Javid, revoked her British citizenship, effectively blocking her return to the UK. She has claimed that Mr Javid’s decision was unlawful because it made her stateless and exposed her to a risk of death. Three judges have now ruled that she should be allowed to return to the UK to fight Mr Javid’s decision in the courts. They said that on her arrival in the UK, she could be detained in custody if there was enough to charge her with terrorist offences. “Ms Begum should be allowed to come to the United Kingdom to pursue her appeal albeit subject to such controls as the secretary of state deems appropriate,” said the judges in a ruling at London’s High Court. The judges said that it was the only way she could have a fair and effective appeal and "that fairness and justice must … outweigh the national security concerns”. An immigration tribunal ruled in February that the government’s decision should stand as Ms Begum was a citizen of Bangladesh "by descent" at the time of Mr Javid's decision and was not stateless. But Bangladesh also refused to allow her into the country saying that she was not a dual citizen and had never visited the country. Speaking after the ruling, Ms Begum’s solicitor, Daniel Furner, said: “Fundamental rights are not extinguished because a person is abroad, or because the allegations against them are serious.” Ms Begum was one of three girls from Bethnal Green Academy in East London, aged 15 and 16, who boarded a flight to Istanbul before making their way to Raqqa in Syria. They followed a schoolmate who travelled the previous year. The young age of the travellers sharpened focus on efforts to prevent disaffected British Muslims from leaving the country to join ISIS amid fears of “blowback” from a generation of radicalised and battle-hardened Britons. A number of fighters have had their citizenship revoked amid a continuing dispute between countries over how best to handle the ISIS activists still alive after defeat on the battlefield. The UK Home Office said the decision was “very disappointing” and would seek to appeal against the ruling. “The government’s top priority remains maintaining our national security and keeping the public safe,” it said.