One Hundred, But Never Plus One

Philosophical debates about open borders or no borders raise an interesting question in my mind, one that I rarely see dealt with. What, I wonder, is the difference between group individual ownership and collective ownership?

Consider the following scenario. There are 100 people, who each have one acre of land to their name. The parcels are contiguous, effectively forming a single 100-acre parcel. It's well-resourced and productive land, and so the 100 people are all doing okay for themselves, but are hampered by the fact that each is working an individual parcel of land with a home on it. So the hundred of them get together one day and decide that they're going to shift things around a bit. They move all of the homes into a small area of the land, say 10 acres. And they'll farm, mine, et cetera, the other 90 acres. But each person retains ownership of their original 1-acre parcel of land. They simply allow the other members of the community more or less free access to it, and effectively barter between each other to keep everything even - so the people who own the acres on which the houses sit collect rents from the people who live in the houses, and at the same time, pay land use fees to the people who own the land that they work on. And this is a contractual agreement - absent either leaving the community and selling out to the others or breaking some sort of agreed-upon rules, neither party may unilaterally break the agreements once they enter into them. The overall result of this agreement is that the land is used more efficiently, and so everyone does noticeably better for being a part of this community of people.

Now, consider a slightly different scenario. The same 100 people live on the same 100 acres. And they decide to concentrate the living areas and the working areas of the land as before. But this time, each person owns privately the small plot of land upon which their home stands, and the rest of the land is "owned" by the community as a whole. Everyone is entitled to use it, so long as they follow the agreed-upon rules. And again, each individual finds themselves better off.

In each case, a 101st person appears on the scene, and wants to move into this community, as things are better there than they are in the place where the newcomer came from. Everyone says "No." In the first scenario, no one rents the newcomer a parcel of land to build a home on, and no-one rents them any of the working land for them to make a living on. In the second scenario, the group simply unanimously decides not to allow the newcomer in. And, in each case, they are ready to use force to keep the newcomer out. In the first scenario, the person who owns whichever parcel of land the newcomer trespasses on rallies the others to aid in ejecting them, and in the second scenario, a group of the community members take it upon themselves to remove the newcomer from common land.

So. What I want to know is why is the first scenario considered acceptable to open/no borders supporters, but not the second? Why must land be privately owned by a single individual in order to be controlled? Why can 100 individuals own parcels of land, and make completely arbitrary determinations as to who may or may not use, access or live on their individual parcels, but once they decide to pool their land into a common ground, they, as a collective lose that right?

If you approach this from the Right side of the political spectrum, it's easy to simply chalk it up to anti-collectivism, and move on. But it's worth noting that the Left isn't necessarily immune to this formulation, either, as they too can support the idea of private ownership of land, yet feel that there is a moral wrong in closed borders. So I'm curious as to how the understanding that the two ideas are different arises.