The usual answer is that the difference lies in the right to freely leave. But the rules of life in a community can differ so much from the requirements of the outside world that leaving becomes practically impossible. Where would someone who leaves an Amish community, or a communist one, go? They are simply not adapted to life.
Where is the guarantee that some community won’t prepare for an aggressive war against others? Where is the guarantee that anyone wishing to leave the community will be allowed to? Where is the guarantee that someone who has left will be accepted elsewhere?
Anonymous question
States are territorial communities recognized by the leadership of other similar territorial communities as sovereigns over their territory. There can also be territorial communities that are not recognized as sovereigns. For example, condominiums. They may have their own customs, but the state remains the sovereign over that territory. There can be extraterritorial communities. An example is the church. The only church that also has its own state is the Catholic Church. It can be viewed both as an extraterritorial jurisdiction with sovereignty over a small territory and as a state with a very powerful diaspora abroad.
The freedom to leave does not separate communities from the state in any way; it has nothing to do with it here. There can be states with the freedom to renounce citizenship. There can be any other territorial and extraterritorial communities with the freedom to leave. And, similarly, all the same can exist without the freedom to leave. The freedom to leave is the characteristic by which we can judge whether a community is compatible with a libertarian order.
Your concerns regarding guarantees of how decent the order will be in various communities, and how dangerous these orders will be for both the members of the community and those around them, are quite justified, since current sovereign territorial communities aka states cannot provide any such guarantees and regularly demonstrate that such concerns are not groundless.
Today, a state can be coerced into observing propriety in three ways: by the threat of attack from other states, the threat of severing interstate economic ties, and the threat of internal regime instability. In a world without states, similarly, a community that is dangerous to others would have those same incentives to behave decently. So why abolish states at all?
In principle, there is no need. If the vast majority makes constant active efforts to ensure that territorial sovereigns do not violate individual rights, it will be a quite decent world. But in such a world, states would not have the opportunity to fight those who wish to associate in a different manner, for example, within the framework of a contract. Thus, a world of minimal states will inevitably be diluted by extraterritorial associations of people who maintain rules within themselves that are not tied to a territory.
As for the fear that people fleeing a highly exotic community will find themselves completely maladapted to life in a global world, it seems exaggerated to me. There are a huge number of migrants in the world who adapt to life in new conditions, and the easier it is, the more they like these new conditions. So this particular factor is not something to fear. Migrants are dangerous if they become a tool of politics. Purely economic relations benefit all their participants.
