Shamima Begum, who at the age of 15 left London to join Islamic State (IS), has lost the first stage of her appeal against the government's decision to remove her United Kingdom (UK) citizenship.
The 20-year-old was later found in a Syrian refugee camp in February 2019. Former home secretary Sajid Javid stripped her of the UK citizenship later that month, reports BBC.
A tribunal ruled that Shamima could be stripped of her nationality because she had not been left stateless.
A semi-secret court, the Special Immigration Appeals Commission (SIAC), which hears national security cases, said she could instead turn to Bangladesh for citizenship.
Under the international law, it is illegal to deprive nationals of citizenship if to do so would leave them stateless.
The commission concluded that Shamima Begum was "a citizen of Bangladesh by descent", after rejecting her case that she had been left stateless.
Shamima has a claim to Bangladeshi nationality through her mother. Albeit, in February 2019, Bangladesh's ministry of foreign affairs said Shamima was not a Bangladeshi citizen and there was "no question" of her being allowed into the country.
Daniel Furner, Shamima Begum's lawyer, said his client would "immediately initiate an appeal" against the decision "as a matter of exceptional urgency".
He added that the dangers she faced had now increased and "her chance of survival [was] even more precariously balanced than before".
At present, she remains in Camp Roj, a refugee camp in northern Syria.
The commission also ruled that Mr Javid had not exposed Shamima to human rights abuses by leaving her in the camp.
Judge Doron Blum, announcing the decision of the tribunal, said that although there were concerns about how Shamima - in Syria - could take part in the proceedings in London, those difficulties did not mean the home secretary's decision should be overturned.
"[Shamima] left the UK apparently of her own free will some years before the decision - and she was not outside the UK as a result of the decision."
The UK Home Office welcomed the ruling but said "it would be inappropriate to comment further whilst legal proceedings are ongoing".
The case will now move on to consider whether the government had legitimate national security grounds to bar Shamima from coming back to the UK.
Shamima Begum's lawyers, at a hearing in October last year, said she had only professed sympathy for the IS group in media interviews to protect herself and her new-born son who later died in the refugee camp.
Shamima left Bethnal Green in east London for Syria in February 2015 with two school friends. She had crossed the Turkish border within days and eventually reached the IS headquarters at Raqqa. There she married a Dutch convert recruit. They had three children, all of whom died.