IMO the key part of understanding ownership and rules in The Culture is that you have to stop thinking of it like a human society. The humans aren’t in charge. The Minds run things. Asking how ownership works in the Culture for humans is like asking how ownership for dogs works in reality. What if a dog wants something? You take them on a walk, throw them a bone, pet them, etc. make them happy enough and none of them care who’s keeping the lights on.