ETYM Cf. French admissibilité.
Acceptability by virtue of being admissible.

Being permissible, being able to be allowed; legitimacy

Admissibility as a consequence of being permitted.

Lawfulness by virtue of being authorized or in accordance with law.
The justification of a ruling group's right to exercise power.
Principles of legitimacy have included divine right, popular approval, and, in the case of communist parties, an insight into the true meaning of history.