In deciding a case closely watched by free speech groups, the court said a federal law gives immunity from libel suits not only to Internet service providers, like AOL, but also to bloggers and other users of their services.

"Subjecting Internet service providers and users to defamation liability would tend to chill online speech," today's unanimous ruling said.

The decision (http://www.courtinfo.ca....ns/documents/S122953.PDF) is a victory for Internet free speech advocates, who warned that a contrary outcome could have affected users of newsgroups, blogs, listservs, and bulletin boards who enter those forums to discuss the views of others. A loss could even have jeopardized websites run by students to evaluate their professors, said the ACLU and the Electronic Frontier Foundation in friend of court briefs.