I think it's more that vesper currently lays claim to it. whether they actually have it or not is debateable.

If a new guild came into minoc and didn't make friends with the vesperians there would likely be a war, as has happened for years, as you know.

whereas, if a new guild came into minoc and made friends with the vesperians and essentially became a vassal of vesper then eventually they might be able to take it away with time.

basically, people can lay claim to what they like, whether or not they actually own it comes down to might at arms and politics.

so really, any conversation about it is pointless..