The Can-Spam Act of 2003 was updated in 2008. There were several significant changes to the Act.

Here are some direct links for the Can-Spam Act.

While Wikipedia is not an offical authority it does contain a world of information and often simplifies the legal wording, as it does in the case of the Can-Spam Act.

http://www.ftc.gov/opa/2008/05/canspam.shtm

http://en.wikipedia.org/wiki/CAN-SPAM_Act_of_2003