Why An Unconstitutionally Vague Statue Is Held Void ?
In Grayned v. City of Rockford, 408 U.S. 104, 115, 33 L. Ed. 2d 222, 92 S. Ct. 2294 (1972), the United States Supreme Court explained the standards for evaluating whether a statute is unconstitutionally vague:
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." 408 U.S. at 108-09.
The vagueness doctrine "simply means that criminal responsibility should not attach where one could not reasonably understand that his contemplated conduct is proscribed." United States v. Nat'l Dairy Prods. Corp., 372 U.S. 29, 32-33, 9 L. Ed. 2d 561, 83 S. Ct. 594 (1963).
Ordinarily, a complainant must show a law is unconstitutionally vague in all of its applications; thus, "[o]ne to whose conduct a statute clearly applies may not successfully challenge it for vagueness." Parker v. Levy, 417 U.S. 733, 756, 41 L. Ed. 2d 439, 94 S. Ct. 2547 (1974).