President Obama says the US needs to redefine and recalibrate its strategic response to terrorism. From drone strikes to the future of Guantanamo, the Obama administration has consistently struggled to reconcile its stated values with the realities of the so-called war on terror. Stephen Sackur speaks to Harold Koh who was chief legal adviser at the US State Department throughout Obama's first term. Did President Obama betray America's highest ideals in the name of national security?