What is required for an act to be legally recognized as a crime?

For an act to be legally recognized as a crime, it must have been established by precedent or legislation. This means that there are defined laws or legal principles that categorize certain behaviors as criminal. In most legal systems, conduct is not simply deemed a crime based on subjective judgment or public opinion; it requires clear statutes or previous court rulings that outline what constitutes a crime.

The principle behind this is rooted in the concept of legality—people should only be punished for actions that have been clearly defined as criminal by law. This ensures fairness and provides individuals with knowledge of what behaviors are prohibited, which is a cornerstone of a just legal system. A crime's categorization as such must be grounded in the established body of law to maintain order and justice.