Oct. 22 (Bloomberg) -- Craigslist won dismissal of a lawsuit filed by the sheriff of Cook County, Illinois, that accused the classified ads Web site of creating a public nuisance by providing a forum for prostitution services.

U.S. District Judge John F. Grady in Chicago threw out the lawsuit filed by Sheriff Tom Dart, finding that the site was only a conduit for others to publish the ads and wasn’t legally responsible for their content.

“Sheriff Dart may continue to use Craigslist’s website to identify and pursue individuals who post allegedly unlawful content,” Grady said in a 20-page decision posted on the court’s electronic docket yesterday. “But he cannot sue Craigslist for their conduct.”

Craigslist, based in San Francisco, records more than 20 billion page views each month, making its www.craigslist.org the seventh-most visited English-language Internet portal in the world, according to its Web site.

In May, the company agreed to remove an erotic services category from its Internet site, replacing it with more closely monitored adult listings after Dart and Illinois Attorney General Lisa Madigan criticized the company.

Madigan had called it an “Internet brothel.”

Dart, citing an opinion by the Polaris Project, which tracks human sexual trafficking, said in his federal court complaint filed in Chicago in March that Craigslist was the biggest source for prostitution in the U.S.

‘Green Light’

A spokesman for the sheriff, Steve Patterson, said yesterday that his office is reviewing its options in the wake of Grady’s dismissal of the lawsuit.

“We realize that Craigslist has a green light to allow criminal activity to take place on its Web site,” Patterson said.

Susan Best, a Craiglist spokeswoman, said in an e-mail: “We welcome the outcome of Judge Grady’s ruling.”

Grady’s ruling cited for support a 2008 U.S. Appeals Court ruling that exonerated the company from liability for the posting of discriminatory ads for the sale or rental of houses and apartments.

That three-judge panel, also based in Chicago, held that Craigslist is more akin to a telephone company than a newspaper, because it exercised no editorial control over its content, exempting it from U.S. laws banning the publication of ads expressing racial, religious or sex bias when offering housing.

Referring to that U.S. 7th Circuit Court of Appeals case, Grady said, “We cannot treat Craigslist as if it did create those ads.”

The case is Thomas Dart v. Craigslist Inc., 09cv1385, U.S. District Court, Northern District of Illinois (Chicago).

To contact the reporter on this story: Andrew M Harris in Chicago at aharris16@bloomberg.net.

Last Updated: October 22, 2009 00:01 EDT