Legitimacy (n.) is a word that does not apply to any state's history: had time not laundered conquest, we would have to go back to hunter-gatherers, since all of history is illegitimate.
Legitimacy (n.) is never automatic: any power system must argue and prove its case to people before it has any claim to it.
Legitimacy (n.) was split off from legality to bless the bombing of Serbia: illegal for lack of Security Council approval, legitimate because no other way was said to remain.
Legitimacy (n.) granted by a great power can be withdrawn after the fact: Arafat's election counted until Washington turned against him.
Legitimacy (n.) belongs to no commissar, corporate manager or cultural manager who claims the right to manipulate and control us — a conclusion reached in the end on intuition and hope.