Economist Milton Friedman predicted in Newsweek nearly 34 years ago that Richard Nixon's ambitious "global war against drugs" would be a failure. Much evidence today suggests that he was right. But the war rages on with little mainstream challenge of its basic weapon, prohibition. To be sure, Mr. Friedman wasn't the only critic. William Buckley's National Review declared a decade ago that the U.S. had "lost" the drug war, bolstering its case with testimony from the likes of Joseph D. McNamara, a former police chief in Kansas City, Mo., and San Jose, Calif. But today discussion of the war's depressing...