A federal appellate court ruled the mother of a drug addict who died after arranging to purchase heroin on the Experience Project website could not hold the site’s corporate owner liable for her son’s death.

The U.S. Court of Appeals for the Ninth Circuit on Tuesday held the Weston-based Ultimate Software Group Inc. was immune from the lawsuit under the Communications Decency Act. The company was behind the website allowing users to discuss experiences anonymously over the internet and shut down the Experience Project site in April 2016, citing a lack of resources to respond to government information requests.