Here's an article that goes into a lot of the law that is relevant to the investigative techniques mentioned: http://www.michiganlawreview.org/assets/pdfs/107/4/kerr.pdf. Note: the article makes a case in support of the third party doctrine, which justifies many of those investigative techniques, but is very well-researched and presents a pretty balanced view of what the law is in addition to defending that status quo.
Matt Blaze is a really excellent person, and this is a research focus area for him.
For more in the same vein, try "The Eavesdropper's Dilemma" (http://www.crypto.com/papers/internet-tap.pdf). This paper is dear to me for reasons obvious to those who worked with me in the 1990s.
Here's an article that goes into a lot of the law that is relevant to the investigative techniques mentioned: http://www.michiganlawreview.org/assets/pdfs/107/4/kerr.pdf. Note: the article makes a case in support of the third party doctrine, which justifies many of those investigative techniques, but is very well-researched and presents a pretty balanced view of what the law is in addition to defending that status quo.