In 2009, the population of Facebook eclipsed the total population of the United States. As we rely more and more on Facebook as a communications platform, it is important that we also know fully our legal rights and protections.
Digital privacy is often a murky legal area due to outdated or plainly inapplicable laws written in the 1980s, well before the advent of social networking. Sociologist Orin Kerr reports that Electronic Communications Privacy Act (ECPA) and Stored Communications Act (SCA) are the laws largely responsible for safeguarding our privacy online.
Facebook Terms of Service (TOS)
The Facebook TOS makes it clear that unauthorized access of accounts which belong to someone else is a violation of their terms of services and will result in suspension from Facebook.
As mentioned above, the ECPA and SCA are federal laws which protect digital communications. Originally these laws prevented government access to email and other stored messages, but the laws have been broadened to legally protect unauthorized access from private individuals.
Accessing someone's account because you know their Facebook password does not make the unauthorized intrusion legal. It is always against the law to access someone's stored communications without permission.
Accessing someone's digital communications without authorization is prohibited by law, no matter the circumstances.