CCC 1902

Authority does not derive its moral legitimacy from itself. It must not behave in a despotic manner, but must act for the common good as a "moral force based on freedom and a sense of responsibility":²¹ GS 74 # 2.

A human law has the character of law to the extent that it accords with right reason, and thus derives from the eternal law. Insofar as it falls short of right reason it is said to be an unjust law, and thus has not so much the nature of law as of a kind of violence.²² St. Thomas Aquinas, STh I-II, 93, 3, ad 2.