For millions of people around the world -- living on every continent, actually, except Antarctica -- the website craigslist.org has become an indispensable tool in the search for housing. Each month, nearly two million housing ads are posted for free on this website. That is more than the number of ads received by every single newspaper in the United States combined.

A small number of these ads have included discriminatory language that legally could not be published in a U.S. newspaper. But can they be published on a website? A group of lawyers in Chicago says "no."

In 1968, just one week after the assassination of civil rights leader Martin Luther King, Jr., the U.S. Congress passed something known as the "Fair Housing Act." It made it illegal for anyone to refuse to rent or sell a home to someone on the basis of race, religion, or national origin. The act was later amended to add gender, disability, and family status to the list.

Craigslist is a bulletin board for the information age

But according to Laurie Wardell of the Chicago Lawyers' Committee for Civil Rights, that has not stopped more than 200 people in the Chicago area from posting discriminatory ads on Craig's List. "The ads range from ads that are kind of universally shocking -- they say things like 'No Minorities,' 'African-Americans Clash With Me,' (and) 'Ladies Only,'" she says, "to ads that are also illegal, but (are) less shocking. There were many, many ads that said 'No Kids,' or 'Adults Preferred,' and that's illegal under the Fair Housing Act."

Newspapers and magazines are required by law to preview all submitted ads before publishing them and to refuse to publish any ads that contain discriminatory language. But on the website craigslist.org, anyone can hop on at any time and post a discriminatory ad, and the ad will stay there until a user notices it, recognizes it as discriminatory, and flags it for removal.

This is how Craig's List handles the problem of discriminatory ads - it relies on users to police themselves. But Laurie Wardell says that isn't good enough. "That's like a police department's saying, 'We don't have any duty to prevent crime from occurring. But if multiple citizens witness a crime and tell us that a crime has been committed, we'll contact the crook, and we'll tell him that he violated the law.'"

The Chicago Lawyers' Committee for Civil Rights has filed a lawsuit against Craig's List, because the Fair Housing Act explicitly holds publishers responsible for discriminatory ads that have been prepared by third parties. But according to Kurt Opsahl, an attorney for the Electronic Frontier Foundation, websites are not legally considered "publishers."

Opsahl points to a provision in the Communications Decency Act of 1996, which says Internet service providers are not liable for the words and images posted on the web by people using their services. "The rationale was to not hold the soapboxes liable for what the speaker has said," he says. "Congress recognized that in order to foster Internet development, it needed to provide some protection for Internet service providers. It simply would be unfeasible for a service provider to pre-review every post that goes onto the service before it gets posted."

The Chicago Lawyers' Committee disputes that claim, insisting that screening software is available for websites like Craig's List to use. What the committee cannot dispute, however, is the fact that the court system has almost universally rejected the idea that Internet service providers are responsible for their users' speech.

In 2003, for example, a federal court in California dismissed a lawsuit that was filed against the website roommate.com. At issue was a housing ad that essentially told "Black Muslims" not to reply.

According to Jim Buckmaster, the CEO of Craig's List, ads like that are reprehensible. But he says if websites are required to preview ads, the way newspapers are, the Internet will no longer be the dynamic public forum that it has become. "Once a newspaper prints something and distributes it, there's no way to remove it. It's there permanently," Buckmaster points out. "So with a newspaper (the review) has to come before the fact. Whereas an Internet site, where users themselves are empowered to remove an ad as soon as it hits the site, it's not nearly that important. And it's actually very empowering to our community of users that they, themselves, get to take action when they see something that's inappropriate."

But there is no way of knowing how long a discriminatory ad may be up, before it is noticed and removed. And Laurie Wardell of the Chicago Lawyers' Committee says by that point, the person posting the ad may have already found a renter or a buyer. In other words, the Craig's List user may have already been able to break the law, with no consequences.