When Westerners arrived in the caliphate, they would burn their passports, ceremonially rejecting their national identity, and brag of the act on Twitter. Now that the Islamic State, or ISIS, has lost its last stretches of land in Iraq and Syria, hundreds of these Westerners and their children are stuck in camps and prisons in northern Syria and Iraq, often hoping to return to their home countries. Their governments, however, don’t want to take the jihadists back—and are resorting to dubious measures to keep them out.

Take the case of Shamima Begum. In 2015, at the age of 15, Begum and two school friends, both also teenagers, ran away from home in east London and flew to Istanbul. From there, they took a bus to the Syrian border, eventually reaching Raqqa, where they joined ISIS. At the time, the girls epitomized the phenomenon of “jihadi brides:” vulnerable young women groomed by online recruiters to marry Islamist fighters in Syria.

A different picture emerged of Begum and her motives in an interview she gave to The Times this February, after a journalist tracked her down at a sprawling UN camp for internally displaced persons (IDPs) in eastern Syria. Begum explained that she had run away in search of a “perfect family” in ISIS and that she regretted nothing. She also volunteered that having seen a decapitated head in a trash can “didn’t faze” her and, in a later interview with the BBC, suggested that the 2017 Manchester bombing was a “kind of retaliation” for the West’s attacks on ISIS.

Shamima Begum and and two friends at London's Gatwick Airport before flying to Turkey, February 2015 Metropolitan Police / The New Yo​rk Times / Redux

Ten days after arriving in Raqqa in 2015, Begum married a Dutch man who had converted to Islam and become an ISIS fighter. The young couple had three children, all of whom soon died, the third shortly after birth in the camp where Begum landed after fleeing the last remaining ISIS enclave. Begum’s partner, Yago Riedijk, now 27, is being held in a Kurdish detention camp in northern Syria. In an interview with the BBC, Riedijk sent his love to Begum and said that he hoped they would be allowed to return to the Netherlands together.

But that prospect is unlikely. The Dutch government has convicted Riedijk in absentia of joining a terrorist organization, and he is a suspect in a foiled Paris-style terrorist attack on his home city in 2018. His pseudo-marriage to Begum, like all such unions administered by ISIS, isn’t legally valid, so Riedijk and Begum are almost certainly not entitled to family reunification in the Netherlands or anywhere else.

A number of the women known as jihadist brides have witnessed horrific violence and lost children and husbands. Some suffer from posttraumatic stress disorder and other ailments. Many are pregnant or have multiple children born in ISIS-held territory. But among these women are also many who have looted the property of people fleeing ISIS or joined the female hesba—ISIS’ religious police—and tyrannized other Muslim women. Some have bragged about taking women into slavery. In April, a German ISIS returnee, Jennifer Wenisch, who allegedly was a member of the morality police in Fallujah and Mosul, went on trial in Germany for war crimes and the murder of a five-year-old Yazidi girl, whom she and her husband held as a slave in Syria. Begum and others like her now claim that they were mere housewives in Syria, but their social media accounts suggest that some of them may have committed crimes even beyond the act of joining a murderous terrorist organization.

By some estimates, U.S.-backed Kurdish forces across eastern Syria now hold more than a thousand Western men and women like Begum and her partner, along with many children, in prisons and camps. The United States has pressured its European allies to put these detainees on trial in their home countries. Earlier this year, U.S. President Donald Trump tweeted that France, Germany, the United Kingdom, and others should repatriate and prosecute the 800 men from Europe who are among the detained fighters. Otherwise, Trump warned, the men would be freed and likely make their way back to Europe to commit new atrocities there. (Trump, for his part, opposes the repatriation of 24-year-old Hoda Muthana, who traveled to Syria from Alabama in 2014 and whose passport was revoked by the Obama administration in 2016.)

The process of bringing ISIS returnees to trial at home is far from straightforward.

European governments were unmoved, not least because the process of bringing ISIS returnees to trial at home is far from straightforward. In some countries, traveling abroad to join insurgencies in Syria and North Africa was not always a criminal act. Sweden, for example, criminalized such travel only in 2016, which means that any Swedish resident who traveled before then could be charged only for specific crimes committed in the conflict zone. But proof of offenses committed in the conflict zone is difficult to collect, despite the increasing use of refugee testimony and evidence gathered from social media accounts. Most European countries do not allow pretrial detention for more than two to 14 days, and monitoring large numbers of free suspects for extended periods of time has proven difficult. And even when ISIS volunteers are convicted, they pose a problem for European prisons, which must then manage a population of proselytizing fanatics.

For all these reasons, European governments prefer to outsource the prosecutions whenever possible. “Foreign fighters should be brought to justice in accordance with due legal process in the most appropriate jurisdiction,” said a spokesperson for British Prime Minister Theresa May—in other words, not in the United Kingdom. Germany’s Foreign Ministry has acknowledged that German citizens stranded in Syria should, in principle, be brought home, but Heiko Maas, the country’s foreign minister, said that given the unstable security situation, repatriating the detainees would be “extremely difficult” to organize. Austrian authorities have declared it too risky to send consular employees to collect Austrian citizens from detention centers and IDP camps in Syria. In February, France announced that 14 French ISIS combatants taken into custody in eastern Syria would be sent to Iraq for trial.

A soldier of the Syrian Democratic Forces with two alleged ISIS fighters held prisoners, north of Raqqa, Syria March 2017 Rodi Said/REUTERS

But outsourcing justice in this manner is problematic. European law prohibits the extradition of suspects to stand trial in countries where they may face the death penalty or be subjected to inhumane prison conditions. No clear statistics exist for how many Western citizens have been tried in Iraq or what sentences they received, but journalists who have attended court proceedings in Baghdad report rushed trials lasting just ten minutes. Men and women sentenced to death are executed on the spot. Three Belgians and at least 11 French citizens have been sentenced to death by hanging. The French government in January promised to intervene to avoid capital punishment for its citizens but continues to insist they must stand trial where their crimes were committed. The German government, meanwhile, managed to get one woman’s death sentence commuted to life in prison. Authorities in Kurdish-administered northeastern Syria, where there is no death penalty, have also prosecuted thousands of captured ISIS fighters but warn that they lack the capacity to deal with so many prisoners.

Alternative proposals raise their own problems. The Swedish government has suggested establishing an international tribunal specifically for ISIS fighters. But it is not clear where such a tribunal would be located, how suspects would be transferred to stand trial, or whether the court could deal with a caseload of several thousand suspects accused of crimes against humanity. The experience of similar tribunals for crimes against humanity in Rwanda and the former Yugoslavia indicates that the trial process would be time-consuming and expensive.

Journalists who have attended court proceedings in Baghdad report rushed trials lasting just ten minutes, with those sentenced to death being executed on the spot.

For good measure, European governments have begun to strip ISIS travelers of their citizenship to prevent them from coming home. A week after Shamima Begum was found in a Syrian IDP camp, British Home Secretary Sajid Javid revoked her passport. Javid claimed that Begum was eligible for Bangladeshi citizenship, since her mother had a Bangladeshi passport, and would therefore not become stateless. Bangladeshi officials, however, denied that Begum was entitled to citizenship. Even if Begum were able to move to Bangladesh, she would likely face the death penalty for having joined ISIS. Two more British jihadist brides who left to marry ISIS fighters, sisters Reema and Zara Iqbal, have also had their passports revoked. The sisters may be eligible for Pakistani citizenship, but their five children, born under ISIS rule, are likely stateless.

According to The Independent, at least 150 British people have been stripped of their citizenship since 2010, although it is unclear how many cases were directly connected to the Syrian conflict. Australia, Belgium, Denmark, and the United States are also known to have revoked the citizenship of ISIS members and recruiters; several other countries, including Austria, Germany, and Switzerland, have either considered applying the measure or passed laws allowing them to do so.

Stripping ISIS travelers of their passports serves two purposes. The first is revenge. “These people have gone to fight against democracy, freedom and everything Denmark stands for, and they do not belong in Denmark,” Inger Stojberg, the Danish minister for immigration, said in March. That sentiment is shared across much of Europe. The second advantage is caseload control, as the cost of monitoring the returnees already strains the resources of European probation and counterterrorism agencies.

To be sure, courts in Europe have often revoked the citizenship of people convicted of grave crimes such as terrorism, provided the convicted were dual nationals. In cases such as Begum’s, however, states are applying the measure preemptively to avoid having to put the suspects on trial at all.

Revoking the citizenship of ISIS travelers raises legal questions and is bad policy. International human rights law provides that everyone has the right to a nationality and that no person may be deprived of citizenship if that would render him or her stateless. Most national laws, moreover, don’t allow stripping people of their nationality by simple administrative order. In some cases, authorities have been less than diligent about making sure the individual in question has a valid claim to citizenship elsewhere. In late 2018, for instance, a British judge blocked the government’s decision to strip two jihadists of their passports, finding that they had no valid alternative citizenship. As a result, European and U.S. courts may well block or overturn the measure in other cases.

Children at an IDP camp in northeastern Syria, March 2019 Issam Abdallah / REUTERS

Moreover, blocking the return of ISIS travelers by revoking their citizenship does nothing to bring to justice the estimated 1,200 European Union citizens who fought in Syria and Iraq and have already returned home. Few of these returnees have been prosecuted. Last year, a Yazidi refugee who had been held as a sex slave by ISIS told the BBC that she had run into her former tormentor outside a supermarket in Germany.

Nor does stripping people of their passports address the plight of the children they bore while in ISIS-controlled territory. ISIS issued no valid passports, and children born in its territory are de facto stateless. None of the births were legally registered, and many orphaned children are in the care of women who are not their mothers. Polygamous and serial marriages make it difficult to establish parentage, without which claims to citizenship cannot be determined.

Still, Sweden recently repatriated the seven orphaned children of a notorious ISIS fighter, Michael Skramo, giving in to pressure from the children’s grandparents. France initially planned to repatriate some 150 children of French jihadists from Syria and Iraq, but the government, possibly fearing a public outcry, has admitted only a handful of them. Other governments have been even less forgiving. ISIS recruits “turned their backs on Denmark,” said Inger Stojberg, the Danish immigration minister, “so there is no reason for their children to be citizens.”

No easy solutions exist for dealing with the countless ISIS fighters—from Europe and elsewhere—now in the custody of U.S.-backed Kurdish forces. But the situation is highly unstable, and leaving ISIS families in camps and prisons or handing them over to Iraq for execution may not be a viable tactic for much longer. In the Syrian province of Idlib, jihadist groups—including some that are aligned with ISIS—are still waging a guerrilla war against the regime of Syrian President Bashar al-Assad and may decide to fill their ranks by freeing ISIS fighters from Kurdish prisons. U.S. troop numbers in Syria have reportedly decreased, and in the event of a U.S. withdrawal, Turkey and the Assad regime may attack the Kurdish forces, which might no longer be able to keep watch over the detainees.

Leaving children behind in what remains a war zone is not an acceptable option. At least in this case, Trump was right: European governments should bring their citizens back home and prosecute those who committed crimes and atrocities.