Comment by ndriscoll

That was, in fact, what COPA mandated in the US in 1998, and SCOTUS struck it down as too onerous in Ashcroft v. American Civil Liberties Union, kicking off the last 20 years of essentially completely unregulated Internet porn commercially available to children with nothing more than clicking an "I'm 18" button. At the time, filtering was seen as a better solution. Nowadays filtering is basically impossible thanks to TLS (with things like DoH and ECH being deployed to lock that down even further), apps that ignore user CAs and use attestation to lock out owner control, cloud CDNs, TLS fingerprinting, and extreme consolidation of social media (e.g. discord being for both minecraft discussions and furry porn).