I'm not going to claim to be an american law expert, but when the agencies can just say "nope" to evidence against them in said court of law, it becomes hard to claim strong legal protections. I may be wrong and misunderstanding the law, but it does seem like that. And as a shot in the dark here I doubt it got any better after the patriot act.
"Joseph P. Nacchio (born June 22, 1949 in Brooklyn, New York) is an American executive... Nacchio was convicted of insider trading during his time heading Qwest. He claimed in court, with documentation, that his was the only company to demand legal authority for surreptitious mass surveillance demanded by the NSA which began prior to the 11 September 2001 attacks.[1]
He was convicted of 19 counts of insider trading in Qwest stock on April 19, 2007[2] – charges his defense team claimed were U.S. government retaliation for his refusal to give customer data to the National Security Agency in February, 2001.[3] This defense was not admissible in court because the U.S. Department of Justice filed an in limine motion,[4] which is often used in national security cases, to exclude information which may reveal state secrets. Information from the Classified Information Procedures Act hearings in Nacchio's case was likewise ruled inadmissible.[5] " [0]
[0]: https://en.wikipedia.org/wiki/Joseph_Nacchio