WHAT IS THE biggest threat to world trade? Stressed supply-chain managers might say new logistical bottlenecks that have seen the cost of shipping rocket recently. Macroeconomists could offer demand change, notably the depressive effect of a possible renewed pandemic. But those taking a longer view might point to the new order of trade policy, which involves more intimidation, discrimination and ultimately, isolation. In short, the very foundations of the multilateral trading system are under assault, from several directions at once.