The Controlling the Assault of Non-Solicited Pornography and Marketing Act requires unsolicited commercial e-mail messages to be labeled (though not by a standard method) and to include opt-out instructions and the sender's physical address. It prohibits the use of deceptive subject lines and false headers in such messages. The FTC is authorized (but not required) to establish a "do-not-email" registry. State laws that require labels on unsolicited commercial e-mail or prohibit such messages entirely are pre-empted, although provisions merely addressing falsity and deception would remain in place. The CAN-SPAM Act takes effect on January 1, 2004.

The CAN-SPAM Act of 2003 was introduced by Senators Conrad R. Burns (R-MT) and Ron Wyden (D-OR) in April 2003, with minor changes from the previous year's version, S. 630 (2002). Two other bills (S. 1231 and S. 1293) were subsequently merged into it. The final version was approved by the Senate in November 2003 and by the House of Representatives in December 2003, and was signed into law by President Bush on December 16, 2003.