In what appears to be a concession to Microsoft, the bill exempts some advertising e-mail sent by the provider of a free e-mail service to its users. Microsoft runs Hotmail, the largest free e-mail service, in part from computers located in California. Microsoft which opposed very similar legislation proposed in California earlier this year says it now supports the current law.

Murray argued that the new law would have more impact than earlier efforts because it applies to a company whose product is advertised, not just the company that actually sends the e-mail.

"When you go after the advertiser, you don't have the same offshore problems than when you go after the sender," he said. "People selling products have to have a local presence. They have to ship them from somewhere and they need a bank account to get paid."

If such suits prove to be effective, it could well have a significant chilling effect, said Keith Cohn, chief executive of the Vendare Group, a big e-mail marketing firm in Sherman Oaks, Calif.

"If someone could make a claim on me because of what an affiliate did, it may well eliminate all the legitimate stuff because people will be running for the hills."