Conservative lawmakers are concerned that the Biden administration is failing to address China’s evasion of U.S. sanctions on Iranian oil and, worse, that officials could deliberately be turning a blind eye to the violations as a concession to Iran.

Reuters reported this week that Iran’s oil exports to China reached 3.75 million tons, or about 1 million barrels per day, which is a recent record for the period following the Trump administration’s sanctions on Iranian oil purchases that took effect in 2019. Although China never stopped importing oil from Iran, the latest numbers represent a huge increase.

The spike in oil purchases …