How about tobacco?” The question was really a proposed assignment. By then, I had spent many years prosecuting monstrous criminals. A parade of tobacco execs did not seem to me to fit that bill, even if they’d had the temerity to eschew a treacly show of contrition when grilled by lawmakers about the health risks of their wares. This faux pas had the news cycle spinning and editorial pages in high dudgeon. As night follows day, carnal fever gripped our ambitious little piranha tank: visions of headlines as big-name defendants were laid low by swashbuckling government lawyers, not merely doing justice but doing . . . good. That was the zeitgeist.

As Conrad Black has painfully learned, the tune in our Manichean legal theater is called by the progressive vanguard—the media, the academy, and, in particular, the Lawyer Left. A Matter of Principle is Black’s often gripping memoir of his...