California is trying a deceptively simple approach to the problem of junk e-mail: It is about to ban spam.

Gov. Gray Davis said on Tuesday that he would sign into law a bill that outlaws sending most commercial e-mail to anyone in the state not explicitly requested by the recipient. That would make it the most wide-reaching law of any of the 35 other state laws meant to regulate spam — or any of the proposed bills in Congress.

"We are saying that unsolicited e-mail cannot be sent and there are no loopholes," said Kevin Murray, the Democratic state senator from Los Angeles who sponsored the bill.

The law, which would also prohibit companies inside the state from sending unsolicited e-mail, would impose fines of $1,000 for each message, up to $1 million for each campaign.

Moreover, the proponents of the measure say, it promises to carry greater weight than most such laws because it would give individuals the right to file private lawsuits, encouraging action by plaintiff's lawyers even if state prosecutors have other priorities. A similar provision is credited with helping to insure compliance with the federal law against unsolicited faxes.

Marketers vehemently argue that California's approach is misguided because the law will do little, they say, to restrain the shadowy spammers responsible for most of the objectionable messages often relayed through foreign computers.

The new law is similar to one recently enacted in Britain that bans marketing e-mail to people who did not request it. Most other state laws, and the proposed federal law, allow unsolicited e-mail until the recipient asks to receive no more.

Indeed, the California law says users must explicitly agree to receive e-mail from each advertiser. That would appear to ban the preferred marketing strategy of many big advertisers: renting e-mail lists of people who have agreed to receive offers, often as part of a sweepstakes entry.

"We don't differentiate between Disney and Viagra," Murray said. "If you go out and rent a list of e-mail addresses, by definition you are not a legitimate business. You are the person we are trying to stop."

The law is scheduled to take effect on January 1. But it faces several hurdles. Many of the bills pending in Congress would preempt tougher state laws. And it is bound to be challenged on constitutional grounds.

David E. Sorkin, a professor at the John Marshal Law School in Chicago, said that the law probably will survive a claim that it violates the First Amendment, as courts have held that commercial speech deserves lesser protection than private speech. But it could be struck down as an unconstitutional interference with interstate commerce.