In Hoffman Estates v. Flipside, Hoffman Estates (1982) 455 U.S. 489, the United States Supreme Court provided us with useful guidance. In that case, an owner of a shop brought a facial-vagueness challenge to a city's ordinance banning the sale of drug paraphernalia. In rejecting the challenge, the court explained that the degree of vagueness tolerated by the federal Constitution depends in part on the nature of the directive and whether it threatens to interfere with speech. (Hoffman Estates, at pp. 498-499.)