[The cartel of thieves that formed a government are] still thieves, because like any other landowner, they aren't creating any value in return for the value they take.
OK, so one distinction between government and a cartel of thieves, as you see it, are the uses for the money they take as "value in return". So if the same organized thieves use part of the funds to improve their own roads, establish their own concessions and created other infrastructure and services that make it easier for people traveling through the pass, that would take them off the hook, as no longer thieves? Assuming, of course, that no ownership titles were given to others, but were retained only by "the state" (the same gang of thieves that organized, gained acknowledgment and recognition of sovereignty by surrounding countries).
Like you said, "As effectively private landowners, these "governments" are very much the same as the bandit collective "government" in the pass that you described."
You mentioned that each government has "degrees of legitimacy" based on their
"commitment to their legitimate function of securing and reconciling the equal rights of all to life, liberty, and property in the fruits of their labor", but how that actually translates to a reliable "rule of law", one that is not based on subjective or prejudicial interpretations is still very unclear to me.
For example, in all cases, whether a democracy, a sheikdom, or a totalitarian dictatorship, a government could, in theory, satisfy all of your requirements of "improvements and a return of value for value taken". Furthermore, in all cases, title will be held by a "sovereign owner", noting that even in a democracy, the "sovereign owner" is, by strict definition, "the majority" - whomever that might be, even if it is mislabeled (falsely, evilly, wickedly, yada yada) as "The People". That, to me, is "private ownership" by any other label. The only difference, in the case of a democracy, for example, is that title transfer can occur by political, rather than economic means.
In all cases, where is the reliable rule of law, given that everyone might describe terms like "legitimacy", "equal", "rights", "liberty", "property", etc., quite differently? In short, and I am asking in earnest - since you give preference to and seem to be more trusting of democratic governments, what mechanism could be in place to prevent "the tyranny of the majority"?