If they don't imprison themsleves, who's going to force them? What do they have to lose by not doing so themselves?
These are the simple questions (with relatively simple answers) you need to ask.
If they have nothing to lose, then why do you expect them to follow the law? Until you give them something to lose, why should you expect them to change their behaviour?
Your post seems to suggest that the default is it working, is that really true? Does it actually work anywhere?
There's also the issue that the executive has all the real power. The courts and congress can send strongly worded letters, the executive has all the guns. This hasn't yet become a direct problem in the US, but it has in many other countries.
You have a structural problem within your country, because the FBI should be clearly working towards arresting the NSA people, for example.
[1]: http://observer.com/2016/09/not-a-single-democrat-held-clint...