One of the most persistent criticisms of President Barack Obama’s counterterrorism policy is that he has not definitively broken with the troubled legacy of George W. Bush. But he could put that judgment largely to rest by pushing to modernize the laws of war. The Geneva Conventions and other similar instruments were designed to deal with traditional armies—not groups with no ties to state sponsors or that operate in failed states. Obama should organize an international conference to establish new standards and agreed-upon interpretations for such subjects as the definition of enemy combatants, the treatment of detainees, and the rendition of suspected terrorists. Drones could also be considered—especially standards to minimize civilian casualties and to establish whether targets pose an imminent threat.

