Legitimacy (noun)

1. The quality of being legally or morally right and acceptable.
2. The quality of having been legally or properly established.
3. The quality of having been officially approved or accepted.

Origin:

From french légitimité, from latin legitimus ("lawful"), from lex ("law").

Examples:

1. The legitimacy of the government was called into question by the opposition.
2. The election was held in a free and fair manner, lending legitimacy to the results.
3. The new law is intended to establish the legitimacy of the new regime.
4. He questioned the legitimacy of the new law.
5. The legitimacy of the company's claim is being investigated.