Well at this point we’re just talking about what clients are doing. But conceivably this could be applied to relays as well. 

I run a relay, relay.nos.social, and a few others, but that’s the main one. I publish both to my relay, and to a proxy that does a blaster to a bunch of public relays that accept writes. 

I could write some extensions for my relay which did this filtering based on mutes and reports, which I’d run on my relay. If you wanted the filters, use my relay. If you don’t like how I run my relay, use any one of the thousand relays.

nostr:npub180cvv07tjdrrgpa0j7j7tmnyl2yr6yr7l8j4s3evf6u64th6gkwsyjh6w6 runs a relay which filters ‘censors’ content so you only get back content from people in the same physical country as you. If you make a request to the relay from Japan, then they’re censoring all non-japanese content. This is good because then you can publish and read content that’s legal in Japan, and you don’t need to care about other countries laws. 

Conceptually there’s no difference from the ‘censoring’ what will show up to each user based on geography vs what’s on a user’s mute list.