Vagueness may invalidate a criminal law for either of two independent reasons. First, it may fail to provide the kind of notice that enables ordinary people to understand what conduct it prohibits; second, it may authorize and even encourage arbitrary and discriminatory enforcement.
Chicago's Gang Congregation Ordinance prohibits "criminal street gang members" from loitering in public places. Under the ordinance, if a police officer observes a person whom he reasonably believes to be a gang member loitering in a public place with one or more persons, he shall order them to disperse. Anyone who does not promptly obey such an order has violated the ordinance. The police department's General Order 92-4 purports to limit officers' enforcement discretion by confining arrest authority to designated officers, establishing detailed criteria for defining street gangs and membership therein, and providing for designated, but publicly undisclosed, enforcement areas. Several cases were filed questioning the constitutionality of the ordinance for violating due process on the basis of vagueness. Two trial judges upheld the ordinance's constitutionality, while eleven others ruled it invalid. On appeal, the Illinois Appellate Court affirmed the latter cases and reversed the convictions in the former. The Supreme Court of Illinois affirmed, holding that the ordinance violates due process in that it is impermissibly vague on its face and an arbitrary restriction on personal liberties. The case was elevated on a writ of certiorari to the Supreme Court of the United States.
Is the ordinance vague?
The Court held that the ordinance was unconstitutionally vague. The ordinance did not meet the fair notice requirement because it did not provide adequate notice of what constituted prohibited conduct. Because no standard of conduct was specified, at all, by the ordinance, the entire ordinance failed to give the ordinary citizen adequate notice of what was forbidden and what was permitted. The ordinance also violated the requirement that a legislature establish minimal guidelines to govern law enforcement. Because the ordinance provided absolute discretion to police officers to determine what activities constituted loitering, the ordinance failed to meet constitutional standards for definitiveness and clarity. Thus, the ordinance was unconstitutional for vagueness.