"On September 17, 2001, President George W. Bush signed a new counterterrorism M.O.N., partly based on Rizzo’s input. It was “multiple pages” in length, according to Rizzo. He had worked at the C.I.A. since 1976 and he regarded this document as the “most comprehensive, most ambitious, most aggressive, and most risky Finding or M.O.N. I was ever involved in.” Among its provisions, “one short paragraph” authorized targeted killings of Al Qaeda terrorists and their allies. “The language was simple and stark.” That paragraph became the foundation for the C.I.A.’s drone operations. George Tenet, the agency’s director at the time, supplemented the M.O.N. with internal guidelines that set down in greater detail how an individual believed to be actively involved in terrorist plots could be nominated and approved for capture or killing. Among other things, the guidelines instructed drone supervisors to avoid civilian casualties “to the maximum extent possible,” according to a former senior intelligence official. It was a decidedly lawyerly and elastic standard."