Having gone through the CAN SPAM act for email marketing, need some further clarification. Their emails are in a public business directory where they have their full details along with emails.
My understanding of CAN SPAM has always been that it is just additional (and national) enforcement of deceptive practices rules. Read the guidelines from the FTC: http://www.business.ftc.gov/documents/bus61-can-spam-act-compliance-guide-business
Which are more readable than the law. They are about truthfulness, disclosure and acting on behalf of the consumer.
So, tell them what you are doing, truthfully. Tell them who you are, and where you are. Offer unsubscribe services, and act on them right away.
I have worked with many clients whose legal guys insisted that everyone must opt-in but I don't see that anywhere. If you follow the basic FTC recommendations and stick to truthful business practices, you can "cold call" with email still.