The collective name of the Electronic Communications Privacy and Stored Wire Electronic Communications Acts, which updated the Federal Wiretap Act of 1968. ECPA, as amended, protects wire, oral and electronic communications while those communications are being made, are in transit, and when they are stored on computers. The act applies to e-mail, telephone conversations and data stored electronically. The USA PATRIOT Act and subsequent federal enactments have clarified and updated ECPA in light of the ongoing development of modern communications technologies and methods, including easing restrictions on law enforcement access to stored communications in some cases.
Link to text of law: Electronic Communications Privacy Act of 1986