Removing Shamima Begum’s citizenship after she fled to Syria left her stateless and at risk of hanging, a court has heard.
Her lawyer said Ms Begum, now 20, is in “an incredibly fragile and dangerous” position in a Syrian refugee camp.
After leaving London as a 15-year-old, Ms Begum lived under the rule of the Islamic State group for three years, before being found in February.
The Home Office denies that the decision left her stateless.
A four-day preliminary hearing is taking place at the Special Immigration Appeals Commission, a semi-secret court where people stripped of British citizenship on national security grounds can challenge the decision.
In submissions to the court, Ms Begum’s lawyers said she had only professed sympathy for the Islamic State group in media interviews to protect herself and her newborn son, who later died in the refugee camp.
Ms Begum’s lawyer, Tom Hickman QC, told the court that she was challenging the decision on three grounds, including whether his client had been made stateless.
He said it also had to decide whether removing her citizenship led to a “real risk of death” or other human rights abuses, and whether she can have a fair and effective appeal given her position in a Syrian refugee camp.
In his written submissions, Mr Hickman said Ms Begum “is not considered a national of Bangladesh and was therefore rendered stateless by the deprivation decision”.
He said she could face the death penalty in Bangladesh, adding: “There have been as many as 2,000 staged killings of individuals suspected of involvement with extremist groups since 2001.”