OLYMPIA, Wash. -- Washington Attorney General Bob Ferguson is asking the U.S. Supreme Court to hear the appeal of a case against Backpage.com, a website accused of promoting child sex trafficking.

Three underage girls, allegedly marketed for sex through Backpage.com, attempted to sue the site and its operators, according to a press release from the attorney general's office. Their lawsuit claimed Backpage’s actions violate both federal and Massachusetts laws prohibiting companies from benefiting financially from promoting or facilitating child sex trafficking.

The courts dismissed the suit, according to the AG's office, citing a provision of the federal Communications Decency Act (CDA) which provides protection to websites that passively post third-party content without altering it.

Using the same provision in 2012, Backpage successfully challenged a Washington state law that added new penalties for posting minors in sex ads.

According to the AG's release, Ferguson said Backpage encourages the use of language that will attract customers looking to prey on children, encourages untraceable payment methods and deletes “sting ads” posted by law enforcement.

The states that have joined Washington are Colorado, Hawaii, Indiana, Kansas, Louisiana, Maryland, Michigan, Minnesota, Mississippi, Montana, Nebraska, New Hampshire, Ohio, Oklahoma, Oregon, Rhode Island, South Carolina, South Dakota, Utah, and Vermont.

For more information on Ferguson’s brief to the Supreme Court click here.