Malum in se is a Latin term that is literally translated to “wrong in itself.” In the legal world, malum in se is generally used in reference to crimes that are fundamentally wrong based on basic principles of morality and the rules of society. This term is differentiated from acts that are considered malum prohibitum, which refers to acts that are wrong because they are deemed to be against that particular society’s custom as mandated by its laws. Generally, the malum in se and malum prohibitum dichotomy is described entirely in the context of criminal law.
Criminal offenses that are malum in se are those that are deemed to be naturally evil simply due to the nature of the act. For example, crimes such as murder, rape, and battery fit this description as they are inherently and objectively wrong acts that have no place in a civilized society. Any crime that is objectively morally reprehensible, as are most crimes defined at common law, is considered malum in se.
As societies develop, rules and regulations beyond those that prohibit crimes that are morally reprehensible are required in order to ensure that the society may continue to properly function. The existence of business entities that form the backbone of the world’s economy require regulation, though violations of those rules and regulations do not strike at the heart of morality and the functioning of a civilized society. Violations of such rules and regulations are differentiated from those that are considered malum in se and are referred to as malum prohibitum, which is literally translated from Latin to “wrong as prohibited.”
Laws that are malum prohibitum are those that are wrong only because a particular law dictates that it is wrong. Malum prohibitum crimes are not limited to those in the business world. A law that requires people to cross the street using a crosswalk, for instance, is an example of a law that is malum prohibitum.
The difference between malum in se and malum prohibitum is not always so cut and dried, however. For example, tax evasion may be a law that straddles the line between malum in se and malum prohibitum. While taxes are a social construct of which the failure to pay does not seem objectively morally reprehensible, there is a fair argument that tax evasion is on par with the malum in se crime of larceny, which involves directly taking the property of another. Many crimes fall within this gray area.