Thousands of lawsuits alleging that social media platforms such as Instagram and TikTok encourage addictive usage can proceed after a U.S. federal appeals court on Monday denied their parent companies’ appeal.

The ruling by the U.S. Court of Appeals for the Ninth Circuit came in response to efforts by Alphabet’s Google; Meta, the parent company of Facebook and Instagram; Snapchat-owner Snap; and ByteDance’s TikTok to reverse a lower California district court decision. 

The social media giants argued that they had immunity under Section 230 of the Communications Decency Act, which shields online service providers from liability for third-party content posted on their platforms. Specifically, the companies claimed that Section 230 bars litigation alleging they failed to warn the public that social media can lead to addictive behavior. 

Google, Meta, Snap and TikTok did not immediately respond to requests for comment.

“Although Section 230 does not expressly provide for immunity from suit, Meta argues that such immunity should be implied. We disagree,” Circuit Judge Jacqueline Hong-Ngoc Nguyen wrote in her opinion.

Social media companies faced a torrent of lawsuits alleging that their design can cause addictive behavior and harm users’ mental health.  

In March, Meta and YouTube were held legally liable for creating products that led to harmful and addictive behavior by young users. TikTok and Snapchat parent Snap were named in the original complaint, but settled before the trial began in late January. The jury in that case awarded $6 million to the lead plaintiff.