The story behind the proposed price cap on Russian oil.

The notion that oil-consuming nations should organize a buyers' cartel to cap the price of oil-promoted by U.S. Treasury Secretary Janet Yellen and recently endorsed by the leaders of the Group of Seven-sounds fanciful. After all, if this were workable, why didn't we do it years ago to bring down oil prices? In fact, this is a creative and perhaps even practical response to two unusual imperatives. The first is well covered by the press: to reduce the flow of oil revenues that are financing Russia's war machine. The second is not: to prevent...