Robert G. Mugabe has ruled over this battered nation, his every wish endorsed by Parliament and enforced by the police and soldiers, for more than 27 years. It appears, however, that not even an unchallenged autocrat can repeal the laws of supply and demand. One month after Mr. Mugabe decreed just that, commanding merchants nationwide to counter 10,000-percent-a-year hyperinflation by slashing prices in half and more, Zimbabwe’s economy is at a halt. Bread, sugar and cornmeal, staples of every Zimbabwean’s diet, have vanished, seized by mobs who denuded stores like locusts in wheat fields. Meat is virtually nonexistent, even for...