Bahison Ravindran says he always believed he was Indian.

Born to Sri Lankan refugee parents in the southern Indian Tamil Nadu state, the 34-year-old web developer had studied and worked there, and held several government-issued identity documents, including an Indian passport.

But a rude shock awaited him in April when police arrested him, saying his passport was invalid.

Authorities said he was not an Indian "citizen by birth" since both his parents were Sri Lankans who had fled to India in 1990 amid the civil war there.

For long, anyone born in India qualified for Indian citizenship, but a 1987 amendment to the law required at least one parent to be an Indian citizen for a child born after 1 July of that year to qualify.