U.S. President Donald Trump’s move to curtail H-1B visas threatens to rewrite the rules for one of India’s biggest business success stories, a decades-old model that’s grown into a $280 billion industry and underpins much of the technology behind the world’s largest corporations. The two Indian software exporters’ shares slid more than 3% on Monday. The abrupt move — a response in part to accusations of abuse — forces Indian Prime Minister Narendra Modi to once again deal with the fallout from "America First" policies. Companies from TCS to Wipro have been hailed as a touchstone of Indian technological achievement, helping create high-skilled jobs for the world’s most populous economy since the idea of outsourced information technology gained currency around the 1990s. Trump deals a blow to some of India’s most valuable companies at a time they’re grappling with IT cutbacks because of geopolitical and economic uncertainty.