Email law that went into effect 12/1/06

I have been looking for information about the email law that went into effect 12/1/06 about users not deleting their email messages from their company email account, even if they are personal emails. I must be using the wrong verbage in the search engines to bring up any kind of articles about this law. Can any one help me out on this, point me in the direction of where I can find articles about it?
thanks so much!