“A decade of war is now ending,” President Obama proclaimed in his second inaugural address. But war is not ending, it is changing — and has been for years. Obama has cut back on heavy-footprint, conventional-force war in two countries. At the same time, he has presided over the rise of a secret, nimbler war defined by covert action, Special Forces, drone surveillance and targeting, cyberattacks and other stealthy means deployed in many countries. This new form of warfare needs a firmer political and legal foundation.

Signs of the new war are all around us. Late Monday a Justice Department “white paper” outlining the president's power to kill U.S. citizens associated with al-Qaeda was leaked to the public. Since the beginning of the year, U.S. drone attacks in Pakistan and Yemen have killed dozens of terrorists, and the government is