The court of appeal ruled this morning that Shamima Begum had been lawfully deprived of her British citizenship. The 24-year-old’s citizenship was first revoked in 2019. She challenged that decision at a special immigration appeals commission last year, and lost. This latest ruling might represent the end of her hope to return home, although given the young woman’s circumstances – all three of her children have died, she lives in a refugee camp they call the “mini caliphate”, and is thought of only periodically by her countrymen in order to be pilloried then forgotten again – it would be foolish to try to guess at her levels of resilience or despair. The judges were careful to stress that the ruling didn’t represent any comment on the sympathy or otherwise it was reasonable to have for Begum – rather, that there was nothing unlawful in Sajid Javid’s deprivation decision. The ruling hadn’t failed to take into account that Begum had been groomed and trafficked, which would have put it in breach of the UK’s anti-slavery protections, and was the contention of her appeal. It’s hard to conceive of what grooming and trafficking mean, if not what happened to Begum, painstakingly documented by Josh Baker in his podcast documentary last year, Shamima Begum – Return from Isis. She left the UK aged 15, and her lawyers highlighted numerous failings of the state – Begum’s school, the Met police, Tower Hamlets council – that even allowed her to get as far as Turkey. Her entry into Syria was reportedly partly facilitated by an informant for Canadian intelligence, so the state failings go beyond even our own. It’s the details once she reached Raqqa, though, that make it absolutely plain her many handlers were motivated by sexual exploitation. She and her two friends, Amira Abase and Kadiza Sultana, were married off to Islamic State (IS) fighters as soon as possible. Abase and Sultana are now dead. Evidently, anti-slavery protections were considered a second order issue to national security: if such protections will only protect you so long as that doesn’t entail any security risk, how protective are they, really? Even in a parallel universe, where 15 is the age of criminal responsibility, and where girls tricked into a brood-mare life of drudgery and control don’t count as trafficked, there are deeper issues that are of grave concern to us all. The first is the idea that Begum cannot return because she poses too great a threat to national security. The notion that the assembled forces of British justice and policing are no match for one 24-year-old, who is easily recognisable and whose whereabouts can presumably be known for the rest of her life, would represent an incompetence so sweeping as to amount to an abnegation of the state’s duty: if it cannot keep us safe from Begum, how would it fare against an adversary who hadn’t renounced fundamentalism and whose identity is not yet known? The second is the assertion in the original case that Begum hasn’t been rendered stateless because she theoretically had access to Bangladeshi citizenship. Jonathan Sumption, the former justice of the supreme court, called this a “legal fiction”; she had never been to Bangladesh, she had no links with the country and it had disowned her anyway. This is the case for many of the people whose citizenship is revoked under the British Nationality Act; they are considered eligible for citizenship elsewhere purely as a legal manoeuvre, with no practical application. It is for parliament to address the problem; the courts cannot take issue with the law. And it is for all of us to consider what this means since the principle is quite stark – it means any one of us with a foreign-born parent has a more contestable and precarious citizenship than those without. You don’t need to have joined a terrorist death cult to find that chilling. Zoe Williams is a Guardian columnist