We often hear the excuse from US-based senders of Unsolicited Bulk Email ("Spammers") that: "My unsolicited bulk mailings comply with the U.S. CAN-SPAM Act which says that sending Unsolicited Bulk Email is not illegal!". In other words, "my spam meets the requirements of US Law therefore I should not be listed for sending it".
The U.S. CAN-SPAM Act does indeed not ban the sending of Unsolicited Bulk Email, it merely outlaws the sending of Unsolicited Bulk Email with false or misleading sender information (and other specified conditions).
The fact that sending Unsolicited Bulk Email, i.e: Spam, is not illegal in the U.S. or any particular country in no way overrides Spamhaus SBL Policy, nor overrides ISP spam filter policies. CAN-SPAM specifically permits all networks and Service Providers, including Spamhaus, to filter (prohibit/reject/block) incoming spam per each network's own policies. Nor does CAN-SPAM override ISP contracts, whose Terms & Conditions of Business (Acceptable Use Policies) all stipulate that sending Unsolicited Bulk Email is prohibited.
If you wish to send bulk marketing communications to Spamhaus users, you must abide by Spamhaus SBL Policy.
The Spamhaus Block List ("SBL") Advisory is a database of IP addresses which do not meet Spamhaus's policy for acceptance of inbound email and therefore from which Spamhaus does not recommend the acceptance of electronic mail. SBL listings are based on Spamhaus' definition of "Spam" meaning "Unsolicited Bulk Email" ("UBE") (see The definition of "spam"). Spamhaus does not evaluate the content or legality of spam, merely whether a message is spam by our definition or not. The responsibility for complying with Spamhaus SBL policy and preventing UBE being sent to Spamhaus users begins and ends with the bulk email sender.