David Edelstein at Foreign Policy grapples with the concept of “international legitimacy” from a realist perspective. Edelstein says that a state views an action as legitimate if it expects to materially benefit, with the occupations of Japan & Iraq provided as contrasting bits of evidence. He gives some slight criticism to Steve Walt, who I think avoids the claimed realist mistake in his post on “cheap talk” (not the game–theorist blog). I think actors whose dominance seems unshakable are accorded more legitimacy and framing something in terms of a completely defeated historical enemy of that actor imparts illegitimacy. The obvious case is World War 2 (“it’s always Munich again!”), which resulted in the U.S becoming the most powerful international actor and eventual “lone superpower” and “world’s policeman” with the end of the Cold War. But the point of all this was just to invite readers to give their thoughts on how perceptions of legitimacy arise. And to what extent does legitimacy affect behavior rather than lip-service/posturing? Does merely possessing the latter not constitute legitimacy at all?
Melendwyr/Caledonian has somewhat related thoughts on power resting on voluntary obedience here.