A U.S. federal appellate court on Monday paved the way for thousands of lawsuits to proceed against Meta Platforms, Alphabet's Google, ByteDance's TikTok, and Snap Inc's Snapchat over allegations that the companies deliberately engineered their social media platforms to be addictive to young users.

The 9th U.S. Circuit Court of Appeals, based in San Francisco, turned down an appeal submitted by Meta and TikTok that sought to overturn a lower court decision requiring the technology companies to defend against more than 3,000 lawsuits filed in federal court. The panel concluded that the companies had brought their legal challenge prematurely.

In their appeal, the tech firms argued that Section 230 of the Communications Decency Act of 1996—a federal statute that generally shields online services from liability related to third-party user content—also prevents lawsuits asserting that the platforms failed to warn the public about their addictive nature.

Under standard legal procedure, most appeals occur after a case has fully concluded with a final ruling or jury verdict. The tech companies contended they should not be required to wait until the conclusion of litigation to challenge the lower court's decision rejecting their immunity defense.

However, the 9th Circuit determined that Section 230 offers a defense against liability rather than broad immunity from being sued, making the early appeal procedurally premature.

The appellate court also denied Meta's request to delay a trial scheduled to begin on Wednesday in a lawsuit brought by 29 state attorneys general. That action alleges the company unlawfully gathered and utilized data from children, designed its social media services to keep young people hooked, and misrepresented consumer safety protections. Meta had argued that the trial should not go forward while its appeal remained pending before the circuit court.

The ruling arrived just days after a state judge in New Mexico determined that Meta had created a public nuisance, ordering the company to pay $567 million into a teen mental health fund and to establish enhanced safety features for youth on its platforms.

A spokesperson for Meta declined to comment on the court's decision.

Representatives for TikTok did not immediately respond to requests for comment regarding the Monday ruling.

Lexi Hazam and Previn Warren, attorneys representing thousands of school districts and individual plaintiffs suing Meta and the other tech platforms in federal court, issued a statement noting that the ruling permits the multistate trial to move forward, along with a trial concerning claims brought by public school districts set for February.

"A trial is how the public finds out what Meta knew about its products' impact on children, when it knew it, and what it chose to do with that knowledge," the attorneys said. "Meta has fought to keep that evidence from the public."

The extensive litigation, brought by state governments, local municipalities, school districts, and individuals, alleges that the social media companies intentionally designed addictive features for young users, contributing to rising rates of depression, anxiety, body-image concerns, and a wider youth mental health crisis across the United States in recent years.

Plaintiffs, including parents, school districts, and state officials, argued that the district court's previous ruling was not a final order and was therefore unappealable at this stage. They also rejected the companies' interpretation of Section 230, arguing the law does not extend protection to claims concerning product design choices and operational practices.

The federal cases have been centralized under U.S. District Judge Yvonne Gonzalez Rogers in Oakland, California, with plaintiffs seeking financial damages, statutory penalties, and restitution. The technology companies had appealed orders issued by Rogers in 2023 and 2024 that largely permitted the legal actions to continue.

In addition to the federal claims, the companies are confronting hundreds of parallel lawsuits in state courts, including approximately 3,300 claims consolidated in a California state court proceeding.

In the first case to reach trial within the California state court litigation—a closely watched test of how juries might respond to similar allegations—a Los Angeles jury in March found Meta and Google negligent for designing social media platforms that inflict harm on youth.

The jury awarded $6 million to a young woman who alleged she became addicted to Instagram and YouTube during her childhood.

The New Mexico public nuisance finding against Meta followed an earlier phase in that case, in which a jury in March directed the firm to pay $375 million after determining it had misled consumers regarding platform safety.

Both Meta and Google, which have denied all allegations across the legal proceedings, stated that they plan to appeal the decisions.