Among the carbon tariff's biggest advocates is Donald Trump's former trade adviser Robert Lighthizer, who favors tariffs in principle. So it's worth deconstructing the misleading arguments that Mr. Cassidy and others are making for climate protectionism.

The bill would impose tariffs on 16 categories of goods produced in countries with higher CO2 emissions than the U.S. They include steel, aluminum, critical minerals, solar panels, wind turbines, crude oil, gasoline, petrochemicals, plastics, paper and lithium-ion batteries. Companies could lobby to have products added to the list, and you can bet they will.