The Obama Administration may not sound like Donald Trump when talking about trade with China, but it isn’t above using protectionism for political gain. On Tuesday the U.S. Commerce Department increased a tariff on “dumped” Chinese cold-rolled steel to 522%, a move that will hurt American manufacturers who need the steel to remain competitive.

The tariff might score some populist points with voters in an election year. It also may be a ploy to get lawmakers to ratify the Trans-Pacific Partnership trade agreement before President...