from
Bouvier's Law Dictionary, Revised 6th Ed (1856)
MALUM IN SE. Evil in itself.
2. An offence malum in se is one which is naturally evil, as murder,
theft, and the like; offences at common law are generally mala in sese.
3. An offence malum prohibitum, on the contrary, is not naturally an
evil, but becomes so in consequence of its being forbidden; as playing at
games, which being innocent before, have become unlawful in consequence of
being forbidden. Vide Bac. Ab. Assumpsit, A, note; 2 Rolle's Ab. 355.