Vagueness Doctrine Law and Legal Definition

Vagueness doctrine is a legal principle which states that a law is unconstitutionally vague if it does not give a "'person of ordinary intelligence a reasonable opportunity to know what is prohibited.” A statute which either forbids or requires the doing of an act in terms so vague that persons of common intelligence must necessarily guess at its meaning and differ as to its application, violates the first essential of due process of law. A statute should state explicitly and definitely what acts are prohibited, so as to provide fair warning and preclude arbitrary enforcement.

The following is an example of a case law on the doctrine:

In the context of a vagueness analysis, the court may impute to persons of common intelligence certain extrinsic knowledge, such as any limiting statutory construction adopted by a court or enforcement agency, general and specialized knowledge regarding the definition of words, and knowledge of legislative history. Consequently, a challenged statute must be clear to persons of common intelligence when viewed in light of this extrinsic knowledge. [Accounting Outsourcing, LLC v. Verizon Wireless Pers. Communs., L.P., 329 F. Supp. 2d 789 (M.D. La. 2004)]