Are there civil rights in cyberspace? Internet sites can legally post discriminatory, false, or libelous information from users. Is it time to better police the Web?

You can find ads for just about anything on Craigslist, an enormous online forum where people post classifieds for everything from garage sales and concert tickets, to job openings and lost dogs. Last July, Craigslist ran an ad for an apartment rental in Chicago that included the following statement: "African-Americans and Arabians tend to clash with me so that won't work out."

If that ad sounds discriminatory to you, you're not alone. Had The New York Times or any other newspaper or magazine published that ad, it would be open to charges of housing discrimination under the federal Fair Housing Act of 1968, which prohibits making housing less accessible to anyone because of their race, gender, or religion.

Yet as the law stands today, according to most legal experts, Craigslist bears no responsibility for what this ad, or others like it, say.

That is the result of a social bargain made 10 years ago, meant to nurture what was then still a strange, fledgling thing called the Internet: Part of the Communications Decency Act of 1996 said that online companies are not liable for transmitting unlawful materials supplied by others.

AMAZON, EBAY & GOOGLE

Now that the Internet has become so integral to life and commerce, is it time to re-examine that bargain? A lawsuit against Craigslist filed by a Chicago fair-housing group in February, citing the "clash with me" ad and more than 100 others, asks that question.

Court decisions so far have almost universally rejected claims against online companies that publish others' speech. Internet companies have been held immune from suits for libel, invasion of privacy, fraud, breach of contract, and housing discrimination.

That means Amazon cannot be sued for its users' millions of reviews of the books and other products it sells. America Online is not responsible for the 6 million new entries posted on its message boards each month. EBay is not liable for damaging statements among the more than 2.4 billion feedback comments its members have posted. And search engines like Google, MSN, and Yahoo do not have to worry that they will be held accountable for the billions of Web pages they make available to their users.

The issue in the current debate is whether online companies should continue to be treated as "common carriers," like FedEx or the phone company, which are not considered responsible for the content of what they transmit. (You can't sue the telephone company because someone called up all your friends and spread a false rumor about you.)

Or should Internet companies be treated like newspapers and magazines? They are held accountable for publishing advertising that others create, as well as for publishing knowingly false or defamatory information about someone or something in their pages.

To put the debate another way: Does it make sense to allow lawsuits against The New York Times and other newspapers for letters to the editor that appear in print, but not for postings from readers that show up on the newspapers' Web sites?

Such immunity for Web sites is too broad, critics argue. James Perry, of the Greater New Orleans Fair Housing Action Center, told Congress during testimony in March that discriminatory postings for housing on the Internet "are perhaps the most concerning issues we have confronted since the hurricanes"--a reference to the storms, including Hurricane Katrina, that caused thousands of people along the Gulf Coast to lose their homes.

The postings, he said, included notices like "not racist but white only" and "prefer white Catholic family."

But Jim Buckmaster, the chief executive of Craigslists, says imposing liability on the site for its users' postings would ruin it.

In a statement on the Craigslist Web site, Buckmaster says the lawsuit, if successful, would "deal multiple blows to everyone's hard-won civil rights--by significantly reducing access to equal-opportunity housing, by undercutting our fundamental free-speech rights, and by intruding on important privacy rights."

VOLUNTARY POLICING

Many Internet companies do voluntarily police at least some of what they transmit, deleting offensive or unlawful messages, often at the prompting of their users.

Craigslist uses a flagging system that allows offensive notices to be deleted. As part of the system, the site adds a warning to every housing posting that discriminatory ads are illegal and gives readers the ability to alert the site if they encounter a discriminatory add.

Buckmaster says that this informal system works better than legally requiring Craigslist, which has 19 employees, to review the almost 2 million ads of unlimited length that it carries each month.

At its heart, the debate is about whether the Internet needs protection to preserve its character as a freewheeling, spontaneous forum. Eugene Volokh, a law professor at the University of California, Los Angeles, says that imposing liability on Craigslist would be a terrible idea; the burdens on the company would be too huge, and the impact would be devastating, not only for that company but for other innovative Internet firms.

But others argue that the unfettered days of the Web should be over, and that if the courts continue to apply the law in the same way, Congress should take action to deal with problematic content on the Web.

Rodney A. Smolla, dean of the University of Richmond School of Law in Virginia, says that child pornography, libelous postings, and terrorist Web sites have already shown the potential of the Web to cause harm.

"The Internet," he says, "has now matured to the point that we are beginning to see that the ordinary rules of law that govern our lives in physical space should also govern our lives in cyber space."

Adam Liptak is national legal correspondent for The New York Times.