Great questions, @novacadian.

Property ownership and the concept of “property” in general in Voluntaryism/libertarianism all starts from the reality of individual self-ownership.

That is to say, you, and no one else, is the captain of your “ship.” When you speak, move your body, etc, it is a direct action. Nobody can do this more directly than you. For all practical intents and purposes, and in all reality, you own yourself.

All humans, unless neurologically damaged, acknowledge this, even if only implicitly. This is why we know things such as murder and violent aggression are wrong. They “steal” or harm someone’s self. Their body.

Property is simply an extension of this self-ownership. Since I own my body, if I use this body and use my time to, say, build a cabin from unowned materials on unowned land, I now have most direct objective link to this cabin. I mixed my body’s labor with the land and raw materials. As such, it is now mine.

Property and ownership, when it comes down to it, aren’t “deemed” by anybody as much as they are direct consequences of reality itself.

As far as who enforces ownership, it could be the owner, it could be a friend or family member of the owner, it could be a complete stranger. In established towns and communities with voluntary systems of governance (non-coercive), it could be some sort of protection firm or private security group.