What I don't understand is why the court would give even a moment's respect to the notion that a legal justification even could, much less does, have 'national security' need for secrecy.
If the existence of a program is public knowledge, and the assertion that it is legal is public knowledge, of what possible harm could the justification for that assertion be?
Is the Al Qaeda sleeper cell in the basement of the capitol building going to conduct a surgical strike against the USC in order to exise a crucial passage and scuttle the entire program? Is the argument even being hinted at that making it easier for congress to amend the laws presently justifying the program would be unacceptable?
I can see that the existence of actual government programs(whether specific actions or broad categories of action) might be a 'national security' thing (although far less often in reality than that excuse is invoked); but applying the notion to legal justifications just seems like a category error, something that could not ever not be absurd even to consider.
I, of course, approve of a decision that the 'national security' justification is inadequate; but it boggles my mind that it would even be considered any more relevant than just a series of nonsense syllables.