Part of the problem is the FISA Court. The court has the power to interpret the constitution, holds secret hearings, the rulings are secret and only government lawyers are allowed.
You can now break the law without even knowing it.
For starters, the law creating FISA isn't something that one can "break", necessarily. The only ones who can run afoul of it are agencies like the NSA, not the populace at large.
More importantly though, the public law carves out a niche that they allow the NSA to operate under, with the proviso that the NSA get the activities pre-approved and overseen by the FISA Court, and with reports routinely made to Congress. The FISA Court verifies that the NSA's proposed activities fall within the scope of the FISA (as amendmended) and with normal case law.
For the approved programs (even the secret ones) they are approved because of the fact that they fall within the area laid out by public law (in the opinion of the FISA Court of course, but that issue underlies all of law).
Even in unclassified jurisprudence there are lots of examples of closed-door court sessions, gag orders, etc.
Now I agree that there are problems with the way the FISA Court is staffed and composed, but those problems don't derive from the closed-door nature as much as from the fact that a single person is able to stack that Court as he/she wishes.
You can now break the law without even knowing it.