I honestly don't understand what do you mean. NSA does everything it does legally, because it's a governmental organisation created to do specifically the thing

I honestly don't understand what do you mean. NSA does everything it does legally, because it's a governmental organisation created to do specifically the thing it does. Yes, you can't do the things NSA do, just like soldiers can carry heavy weapons and you can't. You can argue what they do is immoral, but it almost certainly is legal.