What information you are talking about is important to determine if you are wrong. Hard to tell what is really going on here. From my perspective, you may sound like you are standing on a technicality if you are depriving him of important information. You should talk to company H.R. or your company's lawyer.
It appears you work for a larger company. You should speak with your District/Regional Manager or your company's legal department.
Do not attempt to deal with the former employee's lawyer on your own.