New Delhi, March 4 -- Kolkata: As the sun set on Marquis Street in Kolkata, Mohammad Mazurul Islam, 75, and his wife Rashida Begum, 56, strolled around to check if they had missed out on buying any item from the list that they had made to take back home. They make two annual visits to the city for health checkups, and shop for themselves and their families. The duo were set to return to Gazipur, Bangladesh, the next day.

"It is not like we can return to India any time soon. At least, I cannot," said Begum, whose visa is expiring soon; her husband's tourist visa remains valid for four more years. "We have bought a substantial amount of whole spices, which we usually pack during our visits here. We have also bought shawls, cakes, and choco...