Many Republicans are enraged over revelations in recent days that the Internal Revenue Service targeted conservative nonprofit groups with a campaign of audits and harassment. But of all the troubles now dogging the Obama administration—including the Benghazi fiasco and the Justice Department's snooping on the Associated Press—the IRS episode, however alarming, is also the least surprising. As David Burnham noted in "A Law Unto Itself: The IRS and the Abuse of Power" (1990), "In almost every administration since the IRS's inception the information and power of the tax agency have been mobilized for explicitly...