India, June 25 -- A passport can get an Indian across international borders, secure consular protection in a foreign country and establish nationality before immigration authorities worldwide. Yet, according to officials of the external affairs ministry, it is not a proof of citizenship. The seemingly technical clarification made on Wednesday has revived a long-standing legal question that has acquired renewed significance amid recent controversies over electoral roll revisions and citizenship verification exercises: if even a passport does not conclusively prove citizenship, what document does?

The statement appears counter-intuitive because the Passports Act, 1967, the law governing passports, proceeds on the premise that the holder is...