Legal aid has been granted for Shamima Begum – who joined the Islamic State group aged 15 – to fight the decision to revoke her UK citizenship.
The 19-year-old, who left east London in 2015, was stripped of her citizenship in February, after she was found in a Syrian refugee camp.
Her family has previously said it planned to challenge the decision.
Foreign Secretary Jeremy Hunt said the Legal Aid Agency’s decision to assist Ms Begum made him “very uncomfortable”.
Legal aid is financial assistance provided by the taxpayer to those unable to afford legal representation themselves, whether they are accused of a crime or a victim who seeks the help of a lawyer through the court process.
It is means-tested and availability has been cut back significantly in recent years.
The legal aid that has been granted covers a case before the semi-secret Special Immigration Appeals Commission (SIAC), which adjudicates on cases where the home secretary has stripped someone of their nationality on grounds of national security.
Cases before the Special Immigration Appeals Commission (SIAC) are among the most complicated legal challenges that the government can face.
This is because they typically involve a complex combination of MI5 intelligence reports, which cannot be disclosed to the complainant, and long-standing law on achieving a fair hearing.
It is not yet clear when the case will be heard but the SIAC process can take years to complete – and granting of legal aid in these circumstances is not unusual.
Over the last decade or so there have been many other people stripped of nationality on the basis they are linked to terrorism who have been legally-aided during the SIAC process.
Ms Begum was found in a Syrian refugee camp in February and said she wanted to return home.
Soon afterwards, she gave birth to a boy. He died of pneumonia in March at less than three weeks of age. She had already lost two children.
In the wake of the boy’s death, Home Secretary Sajid Javid was criticised over the decision to strip Ms Begum of her British citizenship.
On Monday, the Daily Mail first reported that legal aid had been granted in response to an application made on March 19.
Dal Babu, a former chief superintendent in the Metropolitan Police and a friend of the family, said Ms Begum should have legal aid to make sure the correct process is followed.
He told BBC Radio 4’s Today programme: “I think legal aid is a principle of the British legal justice system.”
Mr Hunt said: “On a personal level, it makes me very uncomfortable because she made a series of choices and she knew the choices she was making, so I think we made decisions about her future based on those choices.
“However, we are a country that believes that people with limited means should have access to the resources of the state if they want to challenge the decisions the state has made about them and, for obvious reasons, those decisions are made independent from politicians.”