Dozens of UK extremists who joined ISIS could be allowed back into Britain following a court ruling, officials have said.
A woman and her daughters who lost their citizenship on national security grounds for joining the terrorist group should have their British passports reinstated, the High Court in London decided.
The judges said it was unlawful for the government to remove citizenship because the Home Office had not informed her of the move.
Security officials have suggested that the decision could pave the way for other ISIS exiles to return.
The grandmother, labelled D4 in court papers, is currently in the same refugee camp in north-east Syria as Shamima Begum, who left the UK when she was 15 to join ISIS and was also stripped of her British citizenship.
The woman known as D4 was stripped of her British citizenship in 2019 because she and her daughters were suspected of fighting with ISIS in Syria.
According to British government sources, D4, from the north of England, had her citizenship removed two years ago for national security reasons and the court’s decision would have serious implications.
“It will open up the prospect of people judged to be a national security risk being sent back here,” The Sunday Times quoted an official as saying.
It is understood that at least 28 suspected extremists could use the ruling to regain entry to Britain. Up to 1,000 British citizens travelled to the Middle East to join ISIS and other terrorist groups, and about a hundred of them have been stripped of their British citizenship.
The court verdict, which did not dispute grounds for removing citizenship, said the procedure to do so had been unlawful.
“D4 is assessed to have travelled to Syria to align with the proscribed terrorist organisation Islamic State,” the judgment said. But it said the UK Home Secretary Priti Patel’s “failure to give notice of her decision” to deprive D4 of her citizenship “invalidates the order”. It said: “D4 remains a British citizen.”
The Home Office plans to appeal against the decision but if that fails a change in legislation could be required to prevent other ISIS exiles returning to Britain.
“The government will always take the strongest possible action to protect our national security and the priority remains the safety of our citizens,” the Home Office said. “We are carefully considering the implications of this ruling, including an application to appeal.”