BNP Paribas, France’s biggest bank, pleaded guilty in America three years ago to assisting a monstrous regime in east Africa. In 2006, it had helped to finance Sudan’s government, which in turn supported militias that massacred tens of thousands of civilians in Darfur. The firm thereby abetted in genocide and circumvented American sanctions on Sudan. It agreed to pay a fine of $9bn for breaking that embargo, as well as ones on Cuba and Iran. The bank, naturally, hopes to put that grim episode behind it. These days it makes much of its social-responsibility efforts. Its 2015 annual report, for example, trumpeted the financing of a big supermarket in Côte d’Ivoire as typical of its contribution to African development. On July 3rd it named a new head of compliance plus a new “company engagement department”, responsible, among other things, for setting strategy on human rights. Yet the past is hard to banish. The bank now faces scrutiny over an even uglier episode. On June 29th three human-rights groups in France submitted a complaint to a judge, accusing BNP of war crimes and complicity in genocide in Rwanda, in 1994, when 800,000 people, mostly members of the Tutsi minority, were massacred. The groups say that they can prove BNP transferred funds to finance a weapons deal, breaking a UN arms embargo and equipping the killers. The bank has said only that it does not have enough information about the complaint....