The British Nationality Act 1981 gave home secretaries the power to deprive people of British citizenship if their presence was “not conducive to the public good” or if their nationality was gained fraudulently.
But in 2014 the government extended the law to let the power be used even when people would be made stateless, if they have “conducted themselves in a manner seriously prejudicial to the vital interests of the UK”.
“In practice, this power means the secretary of state may deprive and leave a person stateless if that person is able to acquire (or reacquire) the citizenship of another country,” official guidance states.
Hailing the change in November 2014, the then home secretary Theresa May said the power had been used because of terrorist activity in the “overwhelming majority” of cases.