But this excludes what much of the politics and law of England and its colonial offshoots, among many other examples, were for most of their history: divided, non-sovereign governments. Law enforcement with no monopoly of force. There are a number of kinds of such division -- the most familar being federalism and the separation of powers. But the most interesting of all is the unbundling of political property rights.
I have explained why law generally cannot be enforced by purely voluntary relationships. Sure, most rules, formal and informal, of society can be and are followed in a largely voluntary fashion. Reputation and other factors can provide incentives to follow many kinds of rules. But when either the threat or the response become violent or overly fraudulent real law, i.e. law based on local initiations of force, is generally required. Murray Rothbard's fallacy was to try to extend a general principle that succinctly summarizes the substantitve common law -- non-initiation of force -- to the procedural law, which it does not properly summarize and where it mostly does not belong.
Defining "government" as any relationship that is not purely voluntary, what forms of such "government" maximize liberty by minimizing exit costs? Unbundled political property rights put the lie to the "monopoly of force" by unbundling the use of force into a wide variety of specialized forms -- each owned by a particular organization or individual. Here, for example, are some examples of political property rights from medieval and Renaissance England:
There were dozens of standard jurisdictional franchises. For example, "infangthief" enabled the franchise owner to hang any thief caught red-handed in the franchise territory, whereas "outfangthief" enabled the owner to chase the thief down outside the franchise territory, catch him red-handed, and then hang him. "Gallows" enabled the owner to try and punish any capital crime, and there were a variety of jurisdictions correponding to several classes of lesser offenses. "View of frankpledge" allowed the owner to control a local militia to enforce the law. "The sheriff's pleas" allowed the owner to hear any case that would normally be heard in a county court. There were also franchises that allowed the collection of various tolls and taxes.
Modern remnants of such jurisdictions include the shopkeeper's privilege to arrest and imprison shoplifters, "stand your ground" statutes which recapitulate the traditional political property right, liberty of house, citizen's arrest, and so on. Even such a behemoth as the United States has nothing resembling a "monopoly of force."
Political property rights are narrowly defined rights to initiate force -- in very specific ways and in response to specific events and no others. Their legal exercise generally requires the owner to scrupulously follow specific procedures. Unbundled political property rights can reduce exit costs far more than sovereign governments, because they don't come bundled with the power to exclude normally associated with sovereignty and real property (much let the power to prevent people from leaving exercised by the more tyrranous sovereigns). It is thus possible to have a wide variety of jurisdictions enforcing law without any restrictions on the freedom of travel of those acting within the law. But unbundled political property rights do radically violate the nonsensical poli-sci dichotomy of sovereign government vs. anarchy that is taught in schools. Unbundled political property rights are neither sovereign government nor purely voluntary. But they are a crucial part of a world that maximizes liberty.
(This post is expanded from comments I made at Unqualified Reservations).