President Trump’s decision to levy tariffs on China highlights concern about the ongoing role of the WTO and the future of global trade rules.

Kim Jong-un has accelerated North Korea’s buildup of nuclear and other weapons of mass destruction, while also modernizing its large conventional force.

Tariffs have been applied over the years to protect homegrown industries and target competitors who are seen as using unfair trade practices. They impose costs on both importers and exporters and had been in decline until the recent U.S.-China trade war.