how the hell would Microsoft implement a ban on a Minecraft server that Microsoft doesn’t host?

if a minecraft server wants to enforce verification of the game license, the server needs to be in contact with the authentication servers of microsoft. the server operator can turn this off, but then moderation becomes much harder, as usernane based banning becomes useless, and the paywall from ban evasion disappears.

other than that, in recent years there’s something with chat message verification that I think involves sending some of the messages to microsoft? I don’t remember exactly

but also the minecraft client could have a built in blacklist of servers. I don’t know if it has but it’s not much work.
a ban from the authentication server is probably easier though.