AS DONALD TRUMP ramps up tariffs, he is causing turmoil in financial markets. But for a motley group of American manufacturers, the worry is that he may not be going far enough. Specifically, they welcome Mr Trump’s crusade to redraw the rules of international trade but know from experience just how porous tariffs can be. What is needed, they say, is much stricter enforcement at the border to prevent foreign companies from dodging levies.