carte blanche vs authorisation

carte blanche and authorisation both are nouns.

Word	Noun	Adjective	Verb	Adverb
carte blanche	Yes	No	No	No
authorisation	Yes	No	No	No

As nouns, authorisation is a hypernym of carte blanche; that is, authorisation is a word with a broader meaning than carte blanche:

Other hypernyms of carte blanche include authority, authorization, dominance, potency, say-so.

carte blanche (noun)	authorisation (noun)
complete freedom or authority to act	the act of conferring legality or sanction or formal warrant
	the power or right to give orders or make decisions
	official permission or approval
	a document giving an official instruction or command