New Delhi, May 20 -- There are many weapons used in a trade war. The two used most often are complaints to the World Trade Organization or unilateral changes in tariffs against a trading partner, as we have seen with the US and China. Non-tariff trade barriers are often more potent and can be used with relative stealth. One such non-tariff barrier, often used on people-centric industries, is a restriction of the free movement of labour. India still gets about 70% of US H-1B visas issued each year. US consulates in India have considerable latitude. They can act on Washington's orders to tighten up the H-1B regime without any drastic change in US immigration laws. Other similar "work permit" rules in countries such as Australia, Singapore and the UK also vary over time....