India has published a list which effectively strips about four million people in the north-eastern state of Assam of their citizenship.
The National Register of Citizens (NRC) is a list of people who can prove they came to the state by 24 March 1971, a day before neighbouring Bangladesh declared independence.
India says the process is needed to identify illegal Bangladeshi migrants.
Siddhartha Bhattacharya, Assam’s law minister and a member of the BJP, is in no doubt about the fate of those who have been rejected.
“Everyone will be given a right to prove their citizenship,” he told the BBC. “But if they fail to do so, well, the legal system will take its own course.”
That, Mr Bhattacharya clarified, would mean expulsion from India.
At present, correspondents say, that seems little more than a threat aimed at whipping up Hindu support for the BJP ahead of elections.
No deportation procedures have been put in place, and Bangladesh, already burdened by the Rohingya crisis, has shown no sign of being open to accepting a raft of new refugees.