New Delhi, April 3 -- For opponents of free trade, Donald Trump's 'Liberation Day' may seem like 'vindication day.' The world's top power, the US, which generates a quarter of the globe's output, took an inward turn that 'nuked' the aim of open borders for commerce. Globalization, which had long wobbled along, suddenly looks skeletal. America is poised to wall itself off with a steep hike in tariffs to an average level last seen more than a century ago.

It spells a bleak outlook for others.

Trump's bombshell of 2 April won't affect US trade-pact carve-outs of the kind that Canada and Mexico have. But it's grim news on the whole. On 5 April, the US will erect a universal import barrier of 10%. Next, on 9 April, imports from some 60 count...