If a high-level federal bureaucrat wants you dead, you are dead.
That is all you really need to need know of the Department of Justice's white paper on extrajudicial killing. Because once the executive branch claims authority to choose—secretly, uniramerally* and without review—whom to kill and where, it doesn't matter what legal justification it claims gives it that authority, and it doesn't matter what rules it claims to place on its exercise of that authority, because nobody has the power to make it follow the rules, much less refrain from exercising the authority.
As we see in the white paper, the bureaucrats will do what they have to to rationalize murder, including applying doublespeak, so that "imminent" means "not imminent."
Once a bureaucrat (the white paper says "an informed, high-leyel official of the U.S. government," but who decides whether the official is informed? he does) has the power of life and death without outside review, nothing but his good will prevents that power being used in ways of which you would definitely not approve.
I appreciate lawyers' desire to know more about the DOJ rationale: it's the worst law-geek train wreck in history. "Trust in the good will of bureaucrats" is not one of the principles on which the Republic was founded.
*Yes, "uniramerally": consisting of or related to a single branch, as of government. From the Latin ramus, branch. Compare unicamerally, unilaterally.