The phrase "prove legitimacy" is correct and usable in written English.
You can use this phrase when you are referring to an attempt to demonstrate or confirm that something is legitimate or valid. For example, "The artist must prove legitimacy of his identity before proceeding with the purchase of the painting."
The new higher security levels now work in both directions, with you and your bank proving legitimacy to one another.
With a well-run Olympics, the Chinese Communist Party can prove its legitimacy and its continued mandate.
Mr Healey said that Israel had failed to prove the legitimacy of goods suspected of coming from the occupied territories.
The American government gives you a list of things it will be looking for to prove the legitimacy of your love.
With 246 rushing yards and 3 touchdowns in his past two games, Brown faces an opponent today that is also looking to prove its legitimacy.
Registration is not the same as a marriage certificate, but it is a good way to prove the legitimacy of your relationship to employers and insurers, Ms. Hudson said.
Now, analysis of software that the group made freely available to prove its legitimacy suggests that it's authentic, and likely to belong to the National Security Agency.
The Modern Greek state could thus prove its legitimacy and worth as a descendant of the Classical Greek civilization and ensure its independence and a place amongst the civilized Western world.
Kyle Phillips, from the business crime regulatory team at solicitors Slater and Gordon, said: "Criminals caught with large sums of money can normally prove its legitimacy – they don't get caught with tens of millions in the trunk of their car.
He may have been withholding it on principle because no other president had been forced to go to such an extent to prove his legitimacy, but, eventually, the damage being done by withholding became greater than the principle.
