• by Wendy Davis , Staff Writer @wendyndavis, July 6, 2015

Six years ago, Sheriff Tom Dart of Cook County, Ill. sued Craigslist for allegedly creating a public nuisance by allowing users to post prostitution ads.

That lawsuit was quickly thrown out, thanks to the Communications Decency Act -- a federal law that says Web companies and other intermediaries are immune from liability when their services are used to facilitate crimes.

Even though Craigslist won the case, the classifieds site eventually stopped accepting ads for “adult” services. But that didn't end online sex ads. On the contrary, many simply migrated to Backpage.com, which continues to accept them.

Backpage has faced huge pressure to change its policies, but courts have consistently ruled that the company doesn't break any laws by offering users a neutral platform for ads.

As recently as October, three teen sex trafficking victims tried to sue Backpage.com for allegedly facilitating the crimes committed against them. Digital rights groups sided against the teens, arguing that imposing liability on Backpage.com could discourage Web companies from offering platforms where users can post messages, ads or other material.

U.S. District Court Judge Richard Stearns in Boston threw out the case in May, ruling that Web sites don't have to police users' posts.

But that apparently wasn't the last word on Backpage's business. Soon after Backpage prevailed in court, Cook County's Dart turned his attention on the company. This time, instead of going to court, Dart approached Visa and Mastercard directly, asking them to stop processing payments for Backpage.com's adult services.

Both companies reportedly not only agreed to Dart's request, but decided to go even further by terminating all business with the site.

The move riles digital rights advocates, who point out that Backpage.com hasn't violated any laws.

“Human trafficking is a massive human rights issue that deserves focused, dedicated attention from lawmakers, law enforcement, and the public. It’s also a heinous crime that merits severe punishment for those who perpetrate it,” the digital rights group Electronic Frontier Foundation writes today. Backpage, however, is not engaged in human trafficking. It shouldn’t be treated as if it were.”

The EFF adds that payment processors and banks “shouldn’t be in the position of deciding what type of online content is criminal or enforcing morality for the rest of society.”

Santa Clara University law professor Eric Goldman says Dart's decision to pressure Visa and Mastercard to defund Backpage.com places the “basic model of the Internet under attack.”

That's because the Web is built on the principle that neutral intermediaries aren't responsible for crimes by individuals. “People who are the wrongdoers should pay the price,” Goldman says.

The EFF is calling to “strive for neutrality” and reinstate Backpage.com. For now, though, the only payment option for the site's users appears to be Bitcoin.