One thing came through loud and clear in President Trump’s press conference Wednesday with European Commission President Jean-Claude Juncker. When they announced an alliance against third parties’ “unfair trading practices,” they didn’t even have to mention China by name for listeners to know who their target was. Cooperation between the U.S. and EU will squeeze China’s protectionist model, and even before this agreement, there’s been evidence that China is already running up the white flag.

Yes, China is acting tough in...