void-for-vagueness doctrine

noun

: a doctrine requiring that a penal statute define a criminal offense with sufficient definiteness that ordinary people can understand what conduct is prohibited and in a manner that does not encourage arbitrary and discriminatory enforcement

Note: Under the void-for-vagueness doctrine, a vague law is a violation of due process because the law does not provide fair warning of a prohibition and fails to set standards for enforcement that would govern the exercise of the police power.