LONDON — Lawyers representing Shamima Begum, a London schoolgirl who traveled to Syria in 2015 to join the Islamic State, on Tuesday called on Britain’s Supreme Court to allow her to return to her home country to mount her defense, saying she no longer posed a threat.
A decision in the case, which has been hotly debated in Britain after the government said Ms. Begum would be stripped of her British nationality, could leave her stateless, or pave the way for a landmark trial in Britain.
Ms. Begum is seeking to return to Britain to challenge a decision last year by the government of Theresa May, the prime minister at the time, to revoke her citizenship on the grounds that she posed a threat to national security.
David Pannick, one of Ms. Begum’s lawyers, argued on the final day of a two-day hearing at Britain’s highest court that it had been difficult for Ms. Begum to communicate with her lawyers from the camp in Syria where she is being detained, and that she could only properly mount her defense in Britain.
“It cannot be assumed that because Ms. Begum traveled to Syria to join ISIL, she is a continuing threat,” Mr. Pannick added, using an acronym for the Islamic State.
The Supreme Court’s decision is expected at a later date.
Ms. Begum’s case underlines the challenges faced by several European governments, including Britain, France and Germany, that have been reluctant to repatriate citizens who traveled to Islamic State territories, many of whom are now detained in dire conditions by Kurdish forces in northeastern Syria.
Ms. Begum, now 21, boarded a flight from London to Turkey with two friends in 2015 and then entered Syria to join the Islamic State, later marrying a Dutch fighter there and giving birth to three children, all of whom have since died. One of those friends, Kadiza Sultana, is believed to have been killed in an airstrike in Syria in 2016; the fate of the other, Amira Abase, is unknown.
As Islamic State lost control of its last territories in early 2019, a British journalist located Ms. Begum in the al-Hol detention camp in February. She pleaded with the authorities to “re-evaluate my case, with a bit of mercy in their heart,” but Sajid Javid, then the British home secretary, revoked Ms. Begum’s citizenship.
The legal battle that ensued, including the Supreme Court hearing this week, has made Ms. Begum’s case one of the most emblematic among European fighters or militants who joined the Islamic State.
Rights groups and lawyers representing Ms. Begum have raised concerns that she could become stateless if stripped of her British citizenship. Ms. Begum, who was born in Britain and grew up in east London, appealed the decision last year, but a special tribunal ruled that it was lawful because she had the right to become a citizen of Bangladesh through her mother, who holds citizenship of that country.
Under British law, the home secretary can revoke the citizenship of a single-nationality holder if there is “reasonable ground” to believe they can acquire citizenship elsewhere. The Bangladeshi authorities, however, have said that they have no intention of granting Ms. Begum citizenship.
In July, Britain’s Court of Appeal ruled that Ms. Begum could only be granted a “fair and effective appeal” regarding her citizenship if she was able to come back to her home country. The British government appealed that decision, and Ms. Begum’s case was taken up by the Supreme Court.
Ms. Begum has challenged Britain’s decisions to deprive her of citizenship, and to refuse her permission to return to her home country.
James Eadie, a lawyer representing the British government at the Supreme Court hearing, argued on Monday that Ms. Begum had undergone radicalization and “desensitization to violence” during her years with the terrorist group, and that she still posed “a real and current threat to national security.”
Mr. Pannick countered that Ms. Begum had a “statutory right to a meaningful appeal,” which, he argued, “is not subject to any relevant national security exception.”
Tom Hickman, another lawyer acting for Ms. Begum this week, argued on Tuesday that the decision to strip Ms. Begum of her citizenship could violate the European Convention on Human Rights, to which Britain is a signatory.
Ms. Begum is one of two dozen British adults currently detained in Syria and Iraq along with 35 children, according to figures compiled by the Egmont Institute, a Brussels-based research group. Overall, more than 400 Europeans suspected of being militants remain detained there, about 200 of whom are French and about 150 German.
Most reside in the squalid al-Hol camp, where Ms. Begum was previously detained, and where security and humanitarian access has worsened after Turkish forces invaded northern Syria last fall.
There have been multiple reports of violence among residents in al-Hol, as well as attempts by radicalized women to impose Islamic State-style laws in the camp. “Women who now reject militancy are forced to live intermingled with committed jihadists in conditions that enable abuse and intimidation,” the International Crisis Group wrote in January, describing the conditions in the camp as “abysmal.”
Ms. Begum is currently detained in al-Roj, a smaller camp also in northeastern Syria. Earlier this year, Kurdish forces transferred dozens of foreign women and children there from al-Hol, to increase security and improve the detainees’ living conditions.
In al-Roj, Kurdish forces have forbidden the black clothes and full-face coverings worn by members of the Islamic State, according to officials there. About 4,000 people remain in the camp, according to International Crisis Group, compared with tens of thousands in al-Hol.