SAN FRANCISCO, CA — Craigslist and 40 state attorneys general on November 6th agreed to work together to combat “explicit and criminally suggestive ‘erotic services’ ads.” On the same day, a Craigslist user appeared in U.S. District Court to defend himself against interstate prostitution charges arising from ads he posted to the online classified ads site.The defendant, Gregory Fultz of Detroit, and co-defendant Dywon Lever stand accused of operating an illegal prostitution ring that exploited minors in Michigan, Louisiana and Georgia. According to the indictment, the men advertised their services on Craigslist.

They aren’t the first to employ the website for allegedly illegal purposes. In early November, another Detroit man, Robert C. Daniels, we convicted of using Craigslist to operate an interstate prostitution ring that offered underage girls. Prosecutors called some of Daniels’ ads child pornography.

Dozens of other similar cases either have been tried or are on dockets around the country, causing authorities to suggest Craigslist itself might be prosecuted for aiding and abetting criminal activity. In March, Connecticut Attorney General Richard Blumenthal said his office was considering prosecuting Craigslist “for refusing to take aggressive steps to curb apparent prostitution ads.”

That’s what convinced Craigslist to sign the agreement with the attorneys general. The agreement requires the company to collect personally identifiable information, including credit card numbers, from people who post “erotic services” ads, cooperate with law enforcement and the National Center for Missing and Exploited Children, and sue software developers who help miscreants circumvent the site’s anti-child-porn security measures.

Michigan Attorney General Mike Cox declined to sign the accord because he doesn’t believe the agreement goes far enough, according to spokesman Matt Frendewey. The governor’s office has not indicated what terms Cox feels are insufficient or whether the state plans to pursue charges against Craigslist and similar sites.

Child-welfare and anti-porn groups hailed the agreement as a step in the right direction.

“Craigslist has stepped up,” said NCMEC President Ernie Allen. “This is unlawful activity, whether it happens on a street corner, over the telephone or via the internet.”

Craigslist’s chief executive officer assured The Detroit News the website was doing all in its power to ensure the site is clear of illegal content and ads promoting illegal activities.

“Misuse of Craigslist for illegitimate purposes is absolutely unacceptable, and eliminating such misuse is our top priority,” he said, adding that illegal ads compose only a small percentage of the tens of millions of monthly postings.

Detroit’s acting U.S. attorney indicated “safe harbor” provisions the federal Communications Decency Act of 1996 protect internet service providers from civil liability that may arise from user-submitted content. However, the act does not provide criminal immunity.

“The issue is knowledge and intent; you have to have that with every crime,” Terrence Berg told The Detroit News. “If you have that with respect to distribution of child pornography, you have a crime. The question is, does the company know that this stuff is on their network?”

That’s a more complicated issue than it seems at first glance, according to George Washington University law professor Orin Kerr.

“The provider can’t possibly know everything that’s posted on their networks,” Kerr told the News. “The government doesn’t want to prosecute Craigslist. They want to work with Craigslist and have Craigslist take down anything that might violate the law.”