The ethical quandaries are no less daunting: How harshly should a young woman be judged if she didn't participate directly in violence but lent moral support and propaganda value to a jihadist group?
Begum's youthful face has now shaken Britain twice: first in an iconic 2015 image showing her absconding through the Istanbul airport in a weekend getaway outfit, and now again in an image on front pages showing her clad in black robes, begging to be allowed to return.
But public sentiment is unsympathetic to those who voluntarily left the West for Islamic State's proto-state, however traumatised they are today. When Begum and her friends left four years ago, top British police officials promised that if they returned, they would be treated as victims. This week, they made it clear that the offer has expired.
But the refusal to repatriate British citizens, even if legally pragmatic and emotionally satisfying, is irresponsible. Many of Islamic State's European recruits are second-generation children of Arab or Asian immigrants. Abandoning them to their fate or stripping them of citizenship, which the British government has done in some cases, implies that their status as Europeans is contingent. It highlights, for British kids of minority backgrounds, that their Europeanness is fragile; that if they make mistakes, they may not get a second chance.
When Islamic State sought to recruit Western Muslims, it often pointed to the racial discrimination they faced, and whispered to them that they would never truly belong. Repatriating Western Islamic State recruits would acknowledge their Britishness even in the face of atrocities and crime, and could become a powerful way of discouraging the next generation of potential recruits by treating British Muslims in the same way the government would deal with a white adolescent drawn into neo-Nazi groups - by merging rehabilitation with prosecution.
The public understandably fears that returnees would pose a security threat, but there are legal ways, based on more recent legislation, to deal with that danger. Britain's police and intelligence services are regarded as the finest in Europe, and have extensive protective measures used to monitor citizens who are not imprisoned but are deemed to pose security risks.
British women returning from Syria with children often have them taken away into protective care; access to a child or the prospect of its return is its own powerful leverage, and the state hasn't been shy about using it.
In 2016, I visited a camp in Syria where Kurdish forces were detaining Western women who had joined Islamic State. A commander whose job it was to contact Western officials and ask them to come get their citizens was struck by the passivity and indifference he encountered. "Why won't they take their women back?" he asked me. "If they were my citizens, I would take them." He thought they were mostly just wives who had been tricked, and felt pity for them.
Too much of the public discussion around repatriating Western citizens, male or female, hinges on an assumption that letting them come home is equivalent to leniency or forgiveness. Neither the public nor the legal system need to go that far, and investigations and prosecutions should be expected. Acknowledging the simple fact wayward citizens remain citizens, with rights, is simply conceding a universal principle best articulated by Hannah Arendt: that every human being has "the right to have rights."