WASHINGTON, Oct. 12 -- The Senate voted 100 to 0 in 2022 to keep Russian oil out of the United States. On Sunday, a Republican who was in the chamber for that vote went on national television and asked whether the president had just ignored it.

Sen. Thom Tillis of North Carolina told NBC's Meet the Press that he sees a serious argument that Donald Trump is not following the law. The trigger was Trump's Friday announcement that Russia would send more than 300,000 tons of diesel to American and global markets, a Russian diesel sanctions relief move that Treasury backed with a temporary license the same day.

The dispute is narrower than the politics around it, and that is what makes it hard to dismiss. The Ending Importation of Russian Oil...