One of the Roman poet Juvenal’s best-known lines is quis custodiet ipsos custodes. Who will watch the watchers? Some 2,000 years later, this question is especially relevant for America’s criminal-justice system, given the power wielded by federal prosecutors. Too often their profound authority leads to significant abuse, as demonstrated by the case of Sholom Rubashkin.

Mr. Rubashkin, a 57-year-old father of 10, is the former vice president of Agriprocessors, a kosher food processor based in Postville, Iowa. On May 12, 2008, U.S. Immigration and Customs Enforcement agents raided the company’s plant and arrested hundreds of the firm’s workers who were undocumented immigrants. This led the company to file for bankruptcy several months later.

Shortly thereafter, Mr. Rubashkin was arrested by federal officials and…read more at WSJ