COLUMBIA, SC — South Carolina’s attorney general has given online classified ad service Craigslist 10 days to remove ads the AG feels are pornographic or face a criminal investigation.“It appears that the management of Craigslist has knowingly allowed the site to be used for illegal and unlawful activity after warnings from law enforcement officials and after an agreement with 40 state attorneys general,” South Carolina Attorney General Henry McMaster wrote in a letter to Craigslist chief executive Jim Buckmaster.

Craigslist has said it took a number of steps to curb illegal sexual services ads on the site after a November meeting with 40 AGs. Among the new requirements for “Erotic Services” ads are provision of personally identifiable information and payment for the ads by credit card.

The steps are not enough to satisfy McMaster, who is the first state attorney general to threaten specific legal action against the website and set a deadline for compliance with his terms. In late April, Connecticut Attorney General Richard Blumenthal sent to Buckmaster a letter outlining actions he wanted Craigslist to take in regard to adult ads, but he stopped short of threatening prosecution if his terms weren’t met.

Others among the 40 AGs have mentioned dissatisfaction with Craigslist’s compliance with the November agreement, but none as forcefully as McMaster.

“I think the walls are really closing in on Craigslist,” Illinois Attorney General Lisa Madigan told ABC News. She called the Erotic Services area of the site “nothing more than an Internet brothel.”

Free Speech advocates are not sure the AGs are on firm footing in demanding Craigslist censor what may be protected speech.

[McMaster’s threat] “sounds like posturing on the part of a state official, an effort to use what limited leverage he has over Craigslist,” David Ardia, the director of the Citizen Media Law Project at Harvard University’s Berkman Center for Internet and Society, told ABC News. “I think it’s very unlikely that criminal or civil liability would exist.”

Buckmaster met with the AGs of Illinois, Connecticut and Missouri earlier this week. He later released a statement indicating the talks were positive.

“We are optimistic that our shared concerns can be addressed while preserving the beneficial aspects of Craigslist enjoyed by tens of millions of law-abiding Americans each month, without compromising the quintessentially American values of free speech embodied in our Constitution,” Buckmaster said in the statement.