The Obama administration is nearing completion of a detailed counterterrorism manual that is designed to establish clear rules for targeted-killing operations but leaves open a major exemption for the CIA’s campaign of drone strikes in Pakistan, U.S. officials said…

The adoption of a formal guide to targeted killing marks a significant — and to some uncomfortable — milestone: The institutionalization of a practice that would have seemed anathema to many before the Sept. 11 , 2001, terrorist attacks.

Among the subjects covered in the playbook are the process for adding names to kill lists, the legal principles that govern when U.S. citizens can be targeted overseas and the sequence of approvals required when the CIA or U.S. military conduct drone strikes outside war zones.