India, Oct. 30 -- If you think Donald Trump's tariff policies won't reach your phone, think again. The man who just imposed new levies on everything from electric cars to software could, with a single stroke of a pen, decide that WhatsApp messages from India count as "digital imports". If that happened, India's business communications could grind to a halt overnight.

Meta, which owns WhatsApp, would comply immediately. Whether driven by regulation or diplomacy, the company would follow Washington's lead. Every Indian entrepreneur, trader, doctor, and government worker who relies on the app to coordinate would wake up locked out of their most essential tool. Deliveries would stall, vendors would disconnect, and customer service would free...