The Washington State Supreme Court ruled today that that a lawsuit brought by three young women who were sold for sex on Backpage.com can proceed against the company. The ruling adopts the approach advocated by the Attorney General’s Office in an amicus, or “friend of the court,” brief.

“Today’s decision is an important victory in the long-running fight to combat sex trafficking of minors,” said Attorney General Bob Ferguson. “Our office has been a national leader on this issue for many years and will continue to stand up for victims.”

In a 6-3 decision, the court found that plaintiffs should be allowed to try to prove their claims in court, and remanded the case to trial court, as advocated in the attorney general’s amicus brief.

The three underage plaintiffs allege that the website features paid advertising for prostitutes and children forced into prostitution and materially contributed to at least some of the content that was posted, effectively helping promote victimization of children.

“The plaintiffs before us have been the repeated victims of horrific acts committed in the shadows of the law,” the court wrote in its decision. “They brought this suit in part to bring light to some of those shadows: to show how children are bought and sold for sexual services online on Backpage.com in advertisements that, they allege, the defendants helped develop.”

Washington state tried to take action against the website in 2012, passing Senate Bill 6251, which added new penalties for posting sex ads featuring minors. However, Backpage.com convinced a judge that it was entitled to immunity from the penalties under the 1996 federal Communications Decency Act.

The act was intended to protect Internet service providers from liability for defamatory statements made by their online users and materials posted by third parties. It protects providers of “interactive computer service” under certain circumstances, but attorneys filing the lawsuit allege that Backpage.com is in fact an “information content provider.”

Among other arguments, attorneys filing the lawsuit on behalf of the child victims claim that by labeling the page containing the sex trafficking ads “Escorts,” Backpage.com specifically designed the section to facilitate prostitution.