Air is a common because for all intents and purposes, it is unlimited. But in a submarine it is not, thus the population inside the submarine has to be limited to how much air is needed for the people inside it. But even the air is not entirely a common, because two aircraft cannot occupy the same piece of air, same even here down on the ground, the primary place where even in the garden of eden, there is a scarce resource.

Cheating is an incentive only in a short timescale, in a longer timescale cheating costs everyone. People cheat when they think they can get away with it, when there is a security mechanism, they fear to get caught and rightly so. Some people don't need the disincentive, others do. It is in the best interests of the whole to have security against cheating, this is also why many anarchocapitalists talk about compulsory insurance policies. But they are not compelled in the same way as a government does it, because the exact method is different. There is a concrete piece of property and a specified and concrete set of rules set by the owners. In an anarchocapitalist neighbourhood, we house owners may not own the road, but we pay for it because we need it to get in and out. The rules therefore are collaboratively produced, but can entirely differ between one neighbourhood and another. There will tend to be a convergence about these rules over time.

This makes me think of something too. In network technology, switches and routers, the things that give us the internet, do not have to work under a centralised authority. A simple set of rules that each node operates, rules that have been devised and refined over time in newer generations of hardware, improve the rate of convergence towards agreement about how to govern the traffic. It does not require a central government, but it works best when everyone agrees on the rules. This may seem like splitting hairs but consensus on rules is in the interests of all players, it does not have to be enforced, and protocols for discovering them do not also need to be imposed top down. They emerge best from cooperation.

So just as I said above, it is in the interests of all to have an insurance policy against criminal damage, whatever scale it goes to, up to broad regional military defence. In fact, centralising the control of this leads to corruption, whereas when the alliances are looser and each operator chooses their way of operating on a smaller scale, a broader scale consensus eventually must arise because it simply works.