LONDON — Shamima Begum, who as a schoolgirl left her London home to join the Islamic State in Syria in 2015, lost an effort before Britain’s Supreme Court on Friday that could have allowed her to return home to fight the removal of her citizenship.
The ruling could have far-reaching implications for other Westerners associated with the extremist group, long left to remain in detention camps in northeastern Syria.
Ms. Begum, now 21, hoped to return to Britain to appeal a 2019 decision by the British government to strip her of her citizenship, a move that could render her stateless, and successive court appeals from both sides pushed the case to the country’s top court. On Friday, the Supreme Court’s five judges unanimously dismissed her appeals.
Ms. Begum was 15 when she boarded a flight to Turkey with two friends and entered Syria to join the Islamic State. She married a Dutch fighter and had three children, all of whom have since died.
The decision to strip her of her citizenship could leave her stateless. Ms. Begum is a single nationality holder, but British authorities have argued that she could claim Bangladeshi citizenship through her mother. (Bangladeshi authorities have said they would not grant citizenship to Ms. Begum.)
Since the Islamic State lost its final foothold in Iraq and Syria in March 2019, more than 60,000 relatives of Islamic fighters have been detained in squalid camps, including 230 women from a dozen European countries, and hundreds more children, according to the Brussels-based Egmont Institute. They have been detained with little legal basis, and in the case of Britain, the withdrawal of the women’s citizenship has created further obstacles to their repatriation.
Their lawyers, relatives and right groups have periodically pressured the authorities to bring them home, but most European governments have resisted such calls, wary of the backlash they could face from the public, the challenges they may encounter in prosecuting the women and the threats that returnees could pose.
Countries like France, Belgium or Britain have repatriated some children on a case-by-case basis, but dozens of those who remain stranded in the camps have died from malnutrition, hypothermia or various illnesses. Some have been victims of sexual abuse and abduction, according to human rights groups. A London-based organization has nicknamed the camps “Europe’s Guantánamo,” in a report documenting living conditions there last year.
Human rights experts at the United Nation this month urged 57 states, including Britain, to repatriate the families, citing the “unclear grounds” on which they were detained. Some 10 Frenchwomen also detained in the Roj camp started a hunger strike this week, in an effort to pressure their government to bring them home.
“If some Western nations like Britain are facing difficulties in prosecuting their returnees, it will be as difficult for Kurdish authorities, which have limited evidence that these women have committed crimes,” said Thomas Renard, a researcher at the Egmont Institute. “So, do we keep them in illegal detention forever, without the perspective of a trial?”
In addition to humanitarian concerns, researchers have warned that the consequences of not bringing their citizens home could outweigh the risks posed by their repatriation. Some women have left the camps and are now unaccounted for, which could pose a threat of further radicalization. Lawyers have also argued that repentant women could share valuable information about the Islamic State if interrogated at home.
Around 900 British nationals traveled to Syria and Iraq to join the Islamic State, with hundreds of them having died there. About 450 have since returned, but at least nine men and 16 women, along with around 35 children, remain in Syria, according to the human rights group Reprieve. That includes Ms. Begum, whose case has ricocheted from one British court to another.
By stripping Ms. Begum of her citizenship in 2019, the authorities hoped to prevent her return, but it might have had the opposite effect.
The Court of Appeal ruled in July that the only way Ms. Begum would be able to pursue a “fair and effective appeal” was by returning to Britain. The British government then appealed the ruling, sending the case to the Supreme Court.
At a hearing in November, one of Ms. Begum’s lawyers argued that only in Britain could she properly mount her defense, because it was difficult to communicate with her defense team while she is in Syria.
He also said that the assessment that she might pose a threat upon repatriation needed to be re-evaluated. “It cannot be assumed that because Ms. Begum traveled to Syria to join ISIL, she is a continuing threat,” said the lawyer, David Pannick, using an acronym for the Islamic State.
Of the 450 British citizens who returned home, the authorities have prosecuted around 10 percent, far fewer than have countries like Belgium, France or Germany. That has raised concerns about the level of evidence required to bring those individuals to court.
Many women have argued that they were lured to Syria and Iraq by jihadist figures who radicalized them, and that they were there only to raise their children and did not fight or have responsibilities inside the group. Like Ms. Begum, they have also asked for a second chance.
One of the French women detained in the Roj camp, and who started a hunger strike this week, said in a voice note obtained by The New York Times that she wanted to serve her sentence at home. (The New York Times is not publishing her name because she said she and the other women have received death threats from Islamic State supporters who oppose their desire to return.)
“We want to pay our debt to society for the choice we made to come here,” the woman added. “But it is time that this nightmare ends, and that we come back home.”
Constant Méheut contributed reporting from Paris.