4 Cessante Ratione Legis Cessat Lex Ipsa
In the application of this maxim we must distinguish between common and statute law.
(1) Common law. A legal principle must be read in the light of the reason for which it was established. It must not be carried further than this reason warrants, and if the ratio legis wholly fails, the law will fail also.
(2) Statute law. To statute law the maxim has only a limited application, for such law depends upon the authority of the litera legis. It is only when the letter of the law is imperfect, that recourse may be had to the reason of it as a guide to its due interpretation. The maxim in question, therefore, is valid only as a rule of restrictive interpretation. The complementary rule of extensive interpretation is, Ubi eadem ratio ibi idem jus. See Vangerow, I. sect. 25.