A statute is void for vagueness if it “is so unclear or ambiguous that a reasonable person of average intelligence could not determine its meaning or application.” Of course, that can be said of many statutes, so we need more clarity.

The void for vagueness doctrine is normally applied to criminal statutes, but it applies to civil statutes also.  Thus,

In Grayned v. City of Rockford, 408 U.S. 104 (1972), the U.S. Supreme Court (per Justice Thurgood Marshall) stated:

A. Vagueness

It is a basic principle of due process that an enactment is void for vagueness if its prohibitions are not clearly defined. Vague laws offend several important values. First, because we assume that man is free to steer between lawful and unlawful conduct, we insist that laws give the person of ordinary intelligence a reasonable opportunity to know what is prohibited, so that he may act accordingly. Vague laws may trap the innocent by not providing fair warning.  Second, if arbitrary and discriminatory enforcement is to be prevented, laws must provide explicit standards for those who apply them.  A vague law impermissibly delegates basic policy matters to policemen, judges, and juries for resolution on an ad hoc and subjective basis, with the attendant dangers of arbitrary and discriminatory application.  Third, but related, where a vague statute “abut[s] upon sensitive areas of basic First Amendment freedoms,” it “operates to inhibit the exercise of [those] freedoms.”  Uncertain meanings inevitably lead citizens to “`steer far wider of the unlawful zone’ . . . than if the boundaries of the forbidden areas were clearly marked.”

It is this second value that is implicated in vague civil statutes.

In, the Ohio Supreme Court stated:

The Void-for-Vagueness Doctrine

Due process demands that the state provide meaningful standards in its laws. A law must give fair notice to the citizenry of the conduct proscribed and the penalty to be affixed if that law is breached. See, generally, Kolender v. Lawson (1983), 461 U.S. 352, 357-358, 103 S.Ct. 1855, 75 L.Ed.2d 903; Colten v. Kentucky (1972), 407 U.S. 104, 110, 92 S.Ct. 1953, 32 L.Ed.2d 584. Implicitly, the law must also convey an understandable standard capable of enforcement in the courts, Giaccio v. Pennsylvania (1966), 382 U.S. 399, 403, 86 S.Ct. 518, 15 L.Ed.2d 447, for judicial review is a necessary constitutional counterpoise to the broad legislative prerogative to promulgate codes of conduct.  Although the vagueness doctrine is perhaps most familiar in the context of criminal law, “[v]ague laws in any area suffer a constitutional infirmity.” Ashton v. Kentucky (1966), 384 U.S. 195, 200, 86 S.Ct. 1407, 16 L.Ed.2d 469. As the United States Supreme Court has explained:  “Vague laws offend several important values. First,because we assume that man is free to steer between lawful and unlawful conduct, we insist that laws give the person of ordinary intelligence a reasonableopportunity to know what is prohibited so that he may act accordingly. Vague laws may trap the innocent by not providing fair warning. Second, if arbitrary and discriminatory enforcement is to be prevented, laws must provide explicit standards for those who apply them. A vague law impermissibly delegates basic policy matters to police [officers], judges, and juries for resolution on an ad hoc and subjective basis, with the attendant dangers of arbitrary and discriminatory application.” (Footnotes omitted.) Grayned v. Rockford (1972), 408 U.S. 104, 108-109, 92 S.Ct. 2294, 33 L.Ed.2d 222.

When a statute is challenged under the due-process doctrine prohibiting vagueness, the court must determine whether the enactment (1)provides sufficient notice of its proscriptions to facilitate compliance by persons of ordinary intelligence and (2) is specific enough to prevent official arbitrariness or discrimination in its enforcement. Kolender, 461 U.S. at 357, 103 S.Ct. 1855, 75 L.Ed.2d 903. The determination of whether a statute is impermissibly imprecise, indefinite, or incomprehensible, see Buckley v. Wilkins, 105 Ohio St.3d 350, 2005-Ohio-2166, 826 N.E.2d 811, ¶ 19 and Coates v. Cincinnati (1971), 402 U.S. 611, 614, 91 S.Ct. 1686, 29 L.Ed.2d 214, must be made in light of the facts presented in the given case and the nature of the enactment challenged. Hoffman Estates v. Flipside, Hoffman Estates, Inc. (1982), 455 U.S. 489, 495, 102 S.Ct. 1186, 71 L.Ed.2d 362, and fn. 7.

In undertaking that inquiry into the statute or ordinance at issue, the courts are to apply varying levels of scrutiny. “The difference between the various levels of scrutiny for vagueness has never been definitively spelled out, as in equal protection jurisprudence.” ABN 51st St. Partners v. New York (S.D.N.Y.1989), 724 F.Supp. 1142, 1147. Though the degree of review is not described with specificity, regulations that are directed to economic matters and impose only civil penalties are subject to a “less strict vagueness test,” but if the enactment “threatens to inhibit the exercise of constitutionally protected rights,” a more stringent vagueness test is to be applied. Hoffman Estates, 455 U.S. at 498-499, 102 S.Ct. 1186, 71 L.Ed.2d 362.

In either rubric, however, a statute is not void simply because it could be worded more precisely or with additional certainty. State ex rel. Rear Door Bookstore v. Tenth Dist. Court of Appeals (1992), 63 Ohio St.3d 354, 358, 588 N.E.2d 116, citing Roth v. United States (1957), 354 U.S. 476, 77 S.Ct. 1304, 1 L.Ed.2d 1498. The critical question in all cases is whether the law affords a reasonable individual of ordinary intelligence fair notice and sufficient definition and guidance to enable him to conform his conduct to the law; those laws that do not are void for vagueness.  Grayned, 408 U.S. at 108-109, 92 S.Ct. 2294, 33 L.Ed.2d 222; Papachristou v. Jacksonville (1972), 405 U.S. 156, 92 S.Ct. 839, 31 L.Ed.2d 110.

The vagueness doctrine is usually applied in criminal law and First Amendment claims, but neither the rationale underlying the doctrine nor the case law interpreting it suggests that it should not be applied in any case in which the statute challenged substantially affects other fundamental constitutional rights. See Jordan v. De George (1951), 341 U.S. 223, 71 S.Ct. 703, 95 L.Ed. 886 (applying the doctrine to a deportation statute); Giaccio, 382 U.S. at 402, 86 S.Ct. 518, 15 L.Ed.2d 447. And, of course, the Due Process Clause of the Fourteenth Amendment demands that fair notice be given to a property owner in an appropriation action. See, e.g., Walker v. Hutchinson (1956), 352 U.S. 112, 115-117, 77 S.Ct. 200, 1 L.Ed.2d 178 (notice by publication held inadequate in appropriation case). See, also, Lambert v. California (1957), 355 U.S. 225, 229, 78 S.Ct. 240, 2 L.Ed.2d 228 (“Notice is required Before property interests are disturbed, Before assessments are made, Before penalties are assessed”).