Also known as:unconstitutional vagueness · unconstitutionally vague law · void for vagueness · vagueness doctrine
Written by attorneys · grounded in primary & secondary sources — see below
A constitutional defect in a penal statute or ordinance that renders it invalid under the Due Process Clause because it fails to provide fair notice of prohibited conduct or invites arbitrary and discriminatory enforcement by officials.
Sources & Authorities
How it applies
Common Examples
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Loitering Ordinance Dispersal
Uriah Urban stood on a public sidewalk near a retail plaza for twenty minutes checking his phone. An officer approached and ordered him to leave under a city rule targeting anyone remaining in the area with no apparent buying purpose. Uriah sued, claiming the dispersal standard left him unable to predict when his presence would trigger enforcement. The court invalidated the rule because its subjective purpose test supplied no objective guide for citizens or officers.
Attorney Press Statement Rule
Usman Uddin, defense counsel in a high-profile case, told reporters that his client denied all charges. The state bar invoked a publicity rule barring statements with a substantial likelihood of prejudicing the proceeding unless limited to the general nature of the defense. Usman faced discipline because the safe-harbor language offered no clear boundary between permissible and punishable comments. The court struck down the application as unconstitutionally vague for failing to give fair notice of what speech risked sanction.
Select any source to read its text and confirm it supports the definition.
Cases
Casebooks
Dictionaries
Abortion Statute Challenge
Uma Upadhyay, a physician, faced prosecution under a state law regulating when abortions could be performed. The statute used broad terms without defining key medical thresholds or exceptions. Uma sought declaratory relief, arguing the provisions left doctors uncertain about lawful conduct. The court permitted the facial challenge because the law's indeterminate language risked arbitrary enforcement against protected medical decisions.
Roe v. Wade410 U.S. 113 (1973)
Faith Healing Prosecution
Ulf Ulfsson and his spouse relied on prayer rather than medical care for their child under a religious exemption they believed the law permitted. Prosecutors charged them with reckless endangerment after the child died. The couple argued the exemption's scope was too indeterminate to warn them of criminal liability. The court examined whether the statute provided fair warning that their conduct fell outside protected religious practice.
Commonwealth v. Twitchell416 Mass. 114, 617 N.E.2d 609 (1993)
Contraception Ban Challenge
Uriel Urban, a physician, and his patient challenged a state law criminalizing the provision of contraceptives to married couples. The statute contained no definitions clarifying the scope of prohibited medical advice or devices. Uriel argued the broad language chilled protected professional and personal conduct without clear boundaries. The court addressed whether the law's vagueness undermined fair notice of what conduct triggered liability.
Griswold v. Connecticut381 U.S. 479 (1965)
Parental Rights Termination
Una Unger faced termination of her parental rights under a statute requiring proof of permanent neglect. The law used terms such as diligent efforts and failure to plan without further definition. Una argued the standards left parents uncertain what conduct would satisfy or violate the requirements. The court declined to reach the vagueness claim because it had not been preserved below.
Santosky v. Kramer455 U.S. 745, 758-759 (1982)
Common questions
Frequently Asked
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What two requirements must a law satisfy to avoid being unconstitutionally vague?+
A penal law must give ordinary people fair notice of what conduct is prohibited and must supply explicit standards to prevent arbitrary or discriminatory enforcement by officials. When a statute uses indeterminate terms such as no apparent purpose, it fails both requirements because citizens cannot predict enforcement and officers exercise unchecked discretion.
Does internal police training cure a facially vague ordinance?+
No. Unpublished enforcement guidelines cannot supply the fair notice that due process demands from the text of the law itself. A rule turning on an officer's subjective assessment of purpose remains vague even if officers receive internal instructions on how to apply it.
When may a litigant raise a facial vagueness challenge to a statute?+
A party may attack a statute on its face when the law is so unclear that it chills protected conduct or invites arbitrary enforcement across a substantial range of applications. Courts permit such challenges even if the challenger's own conduct might fall within a narrower, clearer prohibition.
How does the vagueness doctrine interact with First Amendment concerns?+
Vague laws that regulate conduct often implicating speech or assembly create an unacceptable risk of chilling protected expression and selective enforcement against disfavored speakers. Courts therefore apply heightened scrutiny to such statutes and invalidate them when the lack of clear standards threatens core constitutional liberties.
410 U.S. 113 (1973)Constitutional Law
…irreparable injury is not applicable where the plaintiff attacks the facial validity of the statute on the ground that it is unconstitutionally vague or overbroad. Pp. 129-166. (b) The constitutional question presented by the challenge to the Texas abortion laws is one of great and immediate public importance, and the Court should not…