I think these questions and answers illustrate the difficulty here, and why ultimately we have the system of countries, governments, laws, armies etc that we do.
For example, in an extreme case anyone can declare their own law and that everything they do is legal under it. This is bound to fail as soon as they infringe significantly on any stronger jurisdiction. Their own law will be irrelevant, and they will be subject to the will of any stronger jurisdiction that chooses to impose on them.
This is because anywhere that two jurisdictions interact is necessarily subject to either mutual consent or rule by force.
This logic quickly extends beyond individuals to any size of grouping under one jurisdiction. Each jurisdiction is sustainable only as far as it is allowed to by all the others. This is no different in quality than what we have now, except that the current system relies heavily on geographical boundaries that have become recognised by historical precedent and on a mutually assuring basis in law and convention. They are also often characterised by deliberative and helpfully slow systems for altering themselves and the boundaries and interactions with others, fascism excepted.
There is nothing wrong with trying to establish alternatives that are not geographically originated and constrained, and I think in principle this is both desirable to some extent, and likely inevitable because of that.
But it is no simple matter to throw off the geographical aspect, and would I think this would be heavily resisted by the existing entities and systems. So it will probably only exist in exceptional circumstances (that I find hard to imagine right now) or in quasi government - contract law for example - and therefore under and within the legal frameworks that we already have.
Perhaps when most things have moved into the quasi government realm there would be a possibility to go the whole hog, but I think it would likely leave (and quite likely require) to exist within a stripped down but still geography based framework of laws, enforcement, and boundary protection that was called upon to administer these functions in behalf of the quasi government systems operating within them.
If so, this really is little different in principle than the relationship we have between contact law and government today. Though over time it could I think be so different n operation and effect as to be almost unrecognisable a compared to what we have now.