Mala prohibita is a legal term that means "wrong because it is prohibited" in its original Latin form. The modern understanding of this term is applied to laws created to reflect a society's morality. These laws control actions that may not be considered crimes by other societies. Generally, these are not crimes to person or property, but things like drug use, copyright infringement, indecent exposure, government criticism and others. What acts are considered mala prohibita often helps explain where a country's philosophical beliefs lie.
Mala prohibita crimes are derived from the common law legal system, which is based on societal customs and appropriate behavior. At one time these violations were taken very seriously by courts and carried severe penalties, but are considered minor offenses in modern society. Due to this standing, most crimes that fall under the mala prohibita classification do not carry stiff penalties for violation.
Most judicial systems classify crimes against person and property, like murder and theft, as serious penalties. A mala prohibita violation is normally seen as a victimless crime or a crime that only harms the offender. An example of a victimless crime that has received a great deal of attention is copyright violation regarding illegal mp3s. Consuming illegal drugs is an example of an act deemed criminal in many societies, but that doesn't harm anyone directly except the user. These types of offenses make these crimes a controversial subject because the illegality of many of these actions can often be interpreted as a personal opinion.
Much like the common law system it bases itself from, many mala prohibita laws change and evolve over time. The common law system in England and France over the last several hundred years evolved to reflect changes in society, much like an unlawful act considered mala prohibita. One example would be the United States' views on alcohol. Once legal, alcohol was prohibited for much the 1920s only to be declared legal again in the 1930s, reflecting changing attitudes on the use of liquor.
American prohibition showed the changing societal views through the country's laws. Mala prohibita crimes remain one way to better understand a society's moralities and beliefs. Depending on the conservativeness or the liberalness of these rules, a tone is set for how a society carries itself via the laws.