Mala in se and mala prohibita, distinguished.
There is a distinction between crimes which are mala in se, or wrongful from their nature, such as theft, rape, homicide, etc., and those that are mala prohibita, or wrong merely because prohibited by statute, such as illegal possession of firearms.
Crimes mala in se are those so serious in their effects on society as to call for almost unanimous condemnation of its members; while crimes mala prohibita are violations of mere rules of convenience
designed to secure a more orderly regulation of the affairs of society.
(Bouvier's Law Dictionary, Rawle's 3rd Revision)