If only restoring history could always be so easy. On a visit to Tripoli this year, Italian Prime Minister Mario Monti returned the 2,000-year-old sculpted head of Domitilla Minor, the daughter of the Roman emperor Vespasian. Stolen from Libya’s northwestern city of Sabratha during the 1960s, the sculpture was immediately put on display by Libyan authorities.

Not all of recent Libyan history will be so easily recovered—nor does everyone want it to be so prominently on show, as this North African country of 6 million starts the uncomfortable task of trying to understand the 42 years of Col....