The unfolding scandal that led to the resignation of Gen. David Petraeus, the Director of the Central Intelligence Agency, started with some purportedly harassing emails sent from pseudonymous email accounts to Jill Kelley. After the FBI kicked its investigation into high gear, it identified the sender as Paula Broadwell and, ultimately, read massive amounts of private email messages that uncovered an affair between Broadwell and Petraeus (and now, the investigation has expanded to include Gen. John Allen's emails with Kelley). We've received a lot of questions about how this works—what legal process the FBI needs to conduct its email investigation. The short answer? It's complicated.