The Delaware Supreme Court has ruled that if an elected official claims they have been defamed by an anonymous blogger, they cannot use a lawsuit to unmask the writer unless he has substantial evidence to prove his claim.

The NY Times reports (reg req) that the court said that it “will more appropriately protect against the chilling effect on anonymous First Amendment Internet speech that can arise when plaintiffs bring trivial defamation lawsuits primarily to harass or unmask their critics.”

The case was bought to the court by Patrick Cahill, a councilman in Smyrna, Delaware, who said he needed the identity of a blogger who in a September 2004 posted that he was divisive and had “an obvious mental deterioration.”

Dare I say that anyone bring a case like this probably does have an obvious mental deterioration.

The court said its decision was the first time any US state or federal Supreme Court had ruled on the rights of anonymous bloggers.