I like rules that generalize. That is to say that I place some special value on non-discrimination in Law. If there must be boundaries on human behavior, then the boundaries must apply equally to everyone in society. No one, no matter their birth nor station should enjoy exemption from the Law. If I'm not allowed to park in front of a fire hydrant, neither shall the Emperor of the Han.
I am the first to admit that this meta-value is idiosyncratic. It comes to me partly from social norms carried over from childhood (fair play on the playground), partly from an affinity I have for the Aristotelian tradition (proportionality uber alles), and partly from a curious American disdain I retain for hereditary political elites (boo titles, boo emoluments of state). Moral intuitions like this are just another turtle: somewhere down the rabbit hole, even the most exacting rationalist is obliged to resort to an aesthetic preference.
To be consistent, shouldn't I extend my fondness for universality to the aesthetics underlying others' meta-values? If someone genuinely believes that a particular few European families have been specially selected by God to enjoy privileges not afforded commoners, or that police should be exempt from the laws they enforce, or that people have no presumption to life or liberty if they happen to be born in another country, by my governing meta-principles, how do I gainsay that? What if a fellow constituent wholly rejects the Original Position thought experiment altogether? What if the set of shared values is null?
When pondering an exchange, non-transaction is perfectly euvoluntary. I wouldn't, for example, purchase a horse saddle at any price: I get no benefit from such a thing and it would take up valuable space in my house. At the tack shop, a gracious "no thank you" is as mutually agreeable as a "yes, please." Politics happens exactly where "no thank you" is not permissible. The closest thing we might imagine to a euvoluntary state would be ruled by unanimity. Such a state would probably be either very small, or very very federalist, neither of which are stable options when the median constituent seeks to consolidate political authority. In theory, I can imagine euvoluntary politics. In practice, my dreams fail me.
When humanity starts to colonize space, it won't be because we seek to live harmoniously among the twinkling stars; it'll be because we're fed up living with these assholes over here. SpaceX: the next best alternative to a Buchanan-Tullock Utopia.