This exists: https://en.wikipedia.org/wiki/Platform_for_Internet_Content_...

It was derided as a "system for mass censorship", and got shot down. In hindsight a mistake, and it should have been implemented - it was completely voluntary by the user.

It’s close, but I see why it failed. There’s no need to include licensing/rights management in there. Also this was before pervasive HTTPS, so it would have been possible for governments and ISPs to snoop the info and possibly block it. If it could be limited to just content ratings, and kept private behind SSL, this isn’t a bad approach.

But this also needs some kind of guarantee that lawmakers won’t try to force it on FOSS projects that want to operate outside the system. And that companies like Google won’t use EEE to gradually expand this header into other areas and eventually cut off consenting adults who want to operate outside this system. I’m not sure if it is possible to get those guarantees.