It annoys, clogs, disrupts and consumes online resources. It has led to lawsuits across the world. Its detractors have formed groups dedicated to limiting or even eradicating it from cyberspace. What is it? Spam.

Virtually any Internet user can attest to the annoying nature of unsolicited commercial e-mail — also called junk e-mail. Each day online marketers send thousands of e-mail messages hawking various products or services.

Individual consumers, Internet service providers and others argue that laws are needed to prohibit this onslaught of bulk electronic mail. They contend that the sheer number of messages consumes too many Internet resources. Groups such as the Coalition Against Unsolicited E-mail — CAUCE — contend that regulating spam is necessary, beneficial and constitutional.

"The First Amendment allows people the right to free speech, but it doesn't guarantee them the right to force others to hear their message," CAUCE writes on its Web site. But others worry that regulations on spam will violate either the First Amendment or the Commerce Clause of the U.S. Constitution. The Commerce Clause prohibits states from burdening or discriminating against interstate commerce. “Because spam is sent interstate via the Internet, it must be regulated in a uniform way at the national level,” writes legal commentator Sabra-Anne Kelin.

Some commentators also contend that at least some restrictions on spam raise First Amendment concerns. As First Amendment attorney Kurt Wimmer writes, “even unsolicited e-mail messages constitute speech.” Flat bans on speech are genuinely viewed with great suspicion in First Amendment jurisprudence. The definition of what exactly is “commercial” in some legislation also raises concerns.

Numerous bills have been introduced in Congress, but it was not until December 2003 that the United States Congress passed an anti-spam measure. Previous measures had cleared one house of Congress or the other but none had cleared both houses.

Congress has considered many proposals over the years, including the Netizens Protection Act of 2001. That bill would require spammers to include their name, physical address and electronic mail address when sending bulk commercial e-mails. The measure would also require spammers to include an opt-out provision enabling recipients to request no further messages. The bill has not made it out of committee.

The Can Spam Act of 2003 became the first federal legislation on the topic when President Bush signed the bill into law on Dec. 16, 2003. The measure prohibits spammers from sending false or misleading header information or deceptive subject headings. It also requires spammers to include a “functioning return electronic mail address” in their e-mails.

The Can Spam law also requires spammers to include a clear identifier that the message is an advertisement and “clear and conspicuous notice of the opportunity” to decline further unsolicited spams. Another provision of the bill requires spammers to “place warning labels on commercial electronic mail containing sexually oriented material.” The law provides that state officials may pursue civil actions against spammers who violate the law.

The law preempts, or supersedes, existing state anti-spam laws that do more than prohibit false and deceptive messages or headings. This has caused some experts to wonder whether the law will be effective. Anita Ramasastry, a law professor at the University of Washington School of Law in Seattle, writes in a column that “in some states, the federal law may even make the spam situation worse. The new law expressly preempts existing state-anti-spam laws — which often provide greater protection for consumers.” She contends that the law may have a negative effect in California because a new law scheduled to go into effect in January 2004 would have prohibited even some truthful spam.

More than 30 states have passed restrictions on spam. The legislation varies greatly from state to state. David Sorkin, arguably the leading authority on the subject, writes: “The legislative responses to spam thus far have ranged in substance from mere disclosure requirements all the way to outright prohibition of unsolicited bulk or commercial e-mail messages.”

Some states have taken a hard-line approach to junk e-mail. For example, Delaware’s law acts as a virtual ban on unsolicited commercial e-mail. The law provides in part: “A person is guilty of the computer crime of failure to promptly cease electronic communication upon request when that person intentionally, recklessly or negligently, fails to stop sending commercial electronic mail to any receiving address or account under the control of any authorized user of a computer system after being requested to do so.”

Other state laws require junk e-mail to be labeled. Tennessee’s law requires the letters “ADV” to be included in the subject line of spam and “ADV-ADLT” for spam of a sexual nature. Many states prohibit the use of false routing information in e-mails. Other laws also require that spammers include opt-out information in the body of the message enabling recipients to send a reply message asking not to receive further messages.

Some state laws have faced constitutional challenges. In 2001, the Washington Supreme Court ruled in State v. Heckel that Washington's state law was constitutional, reversing a lower court that had struck it down on Commerce Clause grounds. The state high court wrote: “We do not believe that the differences between the Act and the anti-spam laws of other states impose extraordinary costs on businesses deploying spam.”

In 2002, the California Supreme Court agreed to review the case Intel Corp. v. Hamidi to determine whether a business could sue a former employee for trespass for sending e-mail messages to many of its employees.

The past several years have shown a continuing increase in legislative responses to spam. Every year numerous provisions are introduced at the federal level and a few more states pass anti-spam legislation. However, as the recent federal legislation acknowledges, legislation is not a cure-all: “The development and adoption of technological approaches and the pursuit of cooperative efforts with other countries will be necessary as well.”