So what we're saying here is that secret memos can now be drafted (retroactively and be backdated if necessary?) that purport to be "legal directives" upon which the telecom companies can claim to have relied in "good faith." Or worse, they may even be able to say they received nothing but oral assurances that their activities were "legal." And if you want to see these "legal directives," it just so happens that since they've been prepared by the Office of Legal Counsel or some other close advisors to the president, executive privilege may just prevent you from doing so.
Or "national security."
Or "I just don't feel like it, and you can't make me."
And that's the real problem here. How is anyone to tell the difference between law that meets the commonly accepted definition we all work with every day on the one hand, and "whatever the hell the president says" on the other?
What is "law," anyway? Is it the stuff that Congress passes in public and that you can read in order to be able to obey it? Or is it just anything that can in practice frighten you into obeying? If you can be sent to jail, or immunized from suit, or whatever, based on a secret showing that you relied in "good faith" on a memo an "administration" official gives you (and literally nothing more -- and perhaps even a lot less), you really have to ask yourself that question. What. Is. Law?