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Glenn,
I think, in evaluating the program, you may be being a little too lawlerly here. Refashioning of the "President's Program" wouldn't have to be, wouldn't even necessarily be about whipping up a new (AUMF) justification. After all, that takes no more time (or effort) than writing a legal brief.
I expect that someday, when all this is revealed, we will find that the refashioning was technological/methodological within the NSA: perhaps adding constraints on the possibility of human intervention prior to the computer screening processes, or perhaps tightening the "degrees of separation" of allowable surveillance or the like. It happened too quickly to be the development and installation of a new computer system. It had to have been more in the nature of flipping switches in, or putting new limits on the capabilities of something that was already built. Now maybe Comey et.al. decided that the AUMF justification also required limitation of what had gone on before, but that conclusion itself would involve technological/methodological changes by the NSA--and it most probably were those that the senior WH thugs, uh staff, were resisting and trying to subvert/supplant.
(You need to pay more attention to how real people actually implement lawyers' and the law's decrees--like how companies build Sarbanes-Oxley compliance mechanisms: this was, most probably, much the same, but in a different context.)