A landmark law that limits children under the age of 16 to one hour per day on social media apps has been blocked by a US court, in a blow to child safety campaigners seeking to limit exposure to sites such as Instagram and YouTube.

In an opinion released on Friday, a federal judge in Virginia halted the enforcement of a bill passed by the state last year, under which social media companies could be fined $7,500 per violation.

The state “does not have the legal authority to block minors’ access to constitutionally protected speech until their parents give their consent by overriding a government-imposed default limit”, Judge Patricia Tolliver Giles wrote of the measure, implementing a preliminary injunction.

Giles concluded the law was “over-inclusive”. Under it, “a minor would be barred from watching an online church service if it exceeded an hour on YouTube . . . yet, that same minor is allowed to watch provider-selected religious programming exceeding an hour in length on a streaming platform,” she wrote. “This treats functionally equivalent speech differently.”

Here is more from the FT.