Generally, the same rules will apply as would be the case for print ads (TIS, TIL, Fair Housing, FDIC membership, etc.) In addition, the CAN-SPAM Act will apply to some of the messages. Those that relate directly to a product or service the customer has already purchased are exempt from CAN-SPAM under the "transaction or relationship message" exemption. Lobby schedule announcements would also fall under that exemption if lobby service relates to the product. The safest (and possibly the cheapest) approach is to treat everything else as covered.
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...gone fishing.