Beijing has good reason to push Seoul to keep its doors open. The motivations are driven less by a belief in free trade and more about the emerging sectors where China is becoming a global leader, areas of South Korean industry most vulnerable to new competition.

Both sides should "maintain stable and smooth industrial and supply chains” between them and the world, Chinese Premier Li Qiang said ahead of the recent trilateral summit that included Japan. "China is ready to work with South Korea to accelerate the second phase of China-South Korea Free Trade Agreement negotiations,” the official Xinhua News Agency cited Li as saying.

In geopolitics, there’s no such thing as free-trade absolutism. Countries pick and choose which counterparts are offered unfettered access and which have tariffs blocking their path. If leaders sense a rival may have a competitive edge, then barriers go up; the U.S. escalation of duties against Chinese electric vehicles and solar cells are one example. China hasn’t been innocent either, raising import taxes on U.S. products in response to the trade war started by the Trump administration.