Ultimately, after Morales challenged his arrest, the Illinois Supreme Court held that the ordinance violated due process of law in that it is impermissibly vague on its face and an arbitrary restriction on personal liberties.

[4] The only issue on certiorari was whether the ordinance was unconstitutionally vague, either on its face or as applied, in violation of "the Due Process Clause of the Fourteenth Amendment to the U.S.

"[2] The United States Supreme Court held in this case that a law cannot be so vague that a person of ordinary intelligence cannot figure out what is innocent activity and what is illegal.

[2][3] Justice John Paul Stevens, writing for the plurality, said that the: ordinance's definition of loitering as "to remain in any one place with no apparent purpose" does not give people adequate notice of what is prohibited and what is permitted, even if a person does not violate the law until he refuses to disperse.

"'[A] law fails to meet the requirements of the Due Process Clause if it is so vague and standardless that it leaves the public uncertain as to the conduct it prohibits,'" noted Justice Stevens, "[i]f the loitering is in fact harmless and innocent, the dispersal order itself is an unjustified impairment of liberty.

Secondly, the Court deemed the ordinance to violate the "requirement that a legislature establish minimal guidelines to govern law enforcement."