Communis error facit jus

The Latin phrase “communis error facit jus” means “common error makes law” in English. This legal principle suggests that if there is a widespread or common misunderstanding or error regarding a particular legal matter, it may be treated as if it were the law, even if it contradicts established legal principles.

This principle is often invoked in situations where there is ambiguity or uncertainty in the law and a consistent practice or belief has developed over time.