Legitimacy is often legalistic but also often moralistic.... There IS, I would argue, a historic correlation between rulership and claims to supernatural moral authority.
I would agree with this and I think it a cogent expansion of my argument.
I would question only one thing and that is, do rulership claims to moral authority have to be based on the supernatural? I'm unsure, having not explored it, but I think you could just drop that word as superfluous, except as an entry to your next paragraph regarding priest-kings, etc.
Therefore I don't think the distinction between legal and moral authority can be neatly drawn;
Neither do I. Actions can be judged as wrong on different levels simultaneously: killing homeless people may be as illegal as it is immoral. However, we know there are differences because there are some things which would be considered immoral but are not illegal (and probably vice-versa).
I do believe that the powerful and those seeking power will use whatever they can to seek power and maintain it. I think there is ample evidence to suggest that morality was and is a tool used for that purpose--whatever basis it has come from.
wr/Geno