Did the spam come from a legitimate email provider, such as constant contact or mailchimp etc? If so, then a complain to them personally, not just pressing report spam will do wonders and may get his account terminated if enough people complain.
Legally, in the US, this is what you do:
What Can I Do With the Spam in my In-Box?
Report it to the Federal Trade Commission. Send a copy of unwanted or deceptive messages to
spam@uce.gov. The FTC uses the unsolicited emails stored in this database to pursue law enforcement actions against people who send deceptive spam email.
Let the FTC know if a "remove me" request is not honored. If you want to complain about a removal link that doesn't work or not being able to unsubcribe from a list, you can fill out the FTC's online complaint form at
www.ftc.gov. Your complaint will be added to the FTC's Consumer Sentinel database and made available to hundreds of law enforcement and consumer protection agencies.
Whenever you complain about spam, it's important to include the full email header. The information in the header makes it possible for consumer protection agencies to follow up on your complaint.
Send a copy of the spam to your ISP's abuse desk. Often the email address is
abuse@yourispname.com or
postmaster@yourispname.com. By doing this, you can let the ISP know about the spam problem on their system and help them to stop it in the future. Make sure to include a copy of the spam, along with the full email header. At the top of the message, state that you're complaining about being spammed.
Complain to the sender's ISP. Most ISPs want to cut off spammers who abuse their system. Again, make sure to include a copy of the message and header information and state that you're complaining about spam.
more:
http://www.ftc.gov/bcp/edu/pubs/consume ... tec02.shtm
As a white hat emailer, I hate spammers with a passion. Report him and persue it seriously.