A federal appeals court on Friday largely upheld a lower-court ruling blocking key provisions of California’s watershed child online safety law, the latest in a series of legal defeats for state officials looking to address concerns that digital platforms pose a risk to children.

The U.S. Court of Appeals for the 9th Circuit in San Francisco ruled that the law’s requirement that tech companies inspect whether their products may harm children before rolling them out — a central part of one of the most significant such laws in the United States — probably violates the First Amendment.