Courts that use the term “content-based” invariably cite to a 1972 case called Police Department v. Mosley, which struck down a Chicago ordinance that banned picketing of schools but made an exception for “peaceful picketing of any school involved in a labor dispute.” Justice Thurgood Marshall wrote for six justices that “above all else, the First Amendment means that government has no power to restrict expression because of its message, its ideas, its subject matter, or its content.” That kind of restriction, the Court has held, triggers a rule of “strict scrutiny” of any viewpoint (“no anti-government speech”) or subject-matter (“no religious speech”) regulations. It’s almost impossible for any law to survive “strict scrutiny,” and laws based—like Gilbert’s—on the need for aesthetic control of roadside signs are unlikely ever to do so.

Since Mosley, the phrase “content-based restriction” has become a shorthand phrase used by lawyers and courts. Until recently, it has meant a restriction or regulation of speech based on the “viewpoint” or the “subject matter” of the speech. The Gilbert code could be viewed as "subject matter" based—but it really isn't. "Meetings" is no more a subject matter than "marketing." The proper way to decide this is that the ordinance is too restrictive, and discriminatory among speakers.

The slow degradation of “viewpoint-subject matter” rule is disconcerting. Justice Anthony Kennedy, in particular, has led the way in this area. In the unfortunate 2011 case of Sorrell v. IMS Health, Inc., he wrote (for six justices) that Vermont could not allow doctors to keep secret details about what drugs they prescribe from pharmaceutical companies seeking to sell them drugs. “The statute ... disfavors marketing, that is, speech with a particular content,” he wrote. The word “content” here has come unmoored. “Marketing” is not a “subject.” It’s an economic activity, to be regulated as needed by the specific market it involves. Kennedy’s foggy version of “content” will—very soon—take us to a place where government can’t regulate advertising at all. Already lower courts have applied the precedent to hold that cigarette companies have a First Amendment right to veto health-warning labels, and drug-company sales reps can encourage doctors to prescribe powerful drugs for unapproved uses.

The federal government is clearly worried that applying the Kennedy formulation to a sign case might gut the Highway Beautification Act of 1965. The act, as amended over the years, discriminates in size and area between kinds of signs, treating “service club signs,” for example, differently from signs advertising that the property they stand on is for sale. The government sides with GNCC in this case, but argues that, “so long as the government’s rationales for the regulation are related to its substantial interests in safety and aesthetics,” the standard should not be looser than strict scrutiny. It argues that the fatal label “content-based” should be reserved for laws that have the purpose or effect of regulating viewpoints or subject matter.

Burma-Shave signs were amusing when I was six, but on balance the highways look a lot better now than in the 1950s. Cluttered highways, however, will be the least of our problems if the Court muffs the “content-basis” question. Powerful forces are targeting all regulation of advertising. A world in which regulation of “marketing” is presumptively unconstitutional might look different, and worse, than the one we live in now.