Susan Porter did what a lot of people do when they see something they support. Or don’t support. She honked her horn. She was cited for her action.

Plaintiff was cited for misuse of a vehicle horn under Section 27001 after she honked in support of protestors gathered outside a government official’s office. Although the citation was dismissed, Porter filed suit to block future enforcement of 27001 against any expressive horn use—including honks not only to “support candidates or causes” but also to “greet friends or neighbors, summon children or co-workers, or celebrate weddings or victories.” She asserted that Section 27001 violates the First and Fourteenth Amendments as a content-based regulation that is not narrowly tailored to further a compelling government interest. Alternatively, she argued that even if the law is not content based, it burdens substantially more speech than necessary to protect legitimate government interests.

California law limits the use of a horn to a safety device, with an exception for car alarms.

.(a) The driver of a motor vehicle when reasonably necessary to insure safe operation shall give audible warning with his horn.

(b) The horn shall not otherwise be used, except as a theft alarm system.

It makes sense. When you hear a horn honk, you look for danger. But even though the citation was dismissed against Porter, the case presented a good vehicle to address the broader question of whether this limitation was a violation of free speech. Why shouldn’t a person, like Porter, be entitled to honk her horn to express support, or disdain, for the conduct of others?

The majority decision also contradicts binding precedent on narrow tailoring. “Precision of regulation must be the touchstone” for restricting speech. Edenfield, 507 U.S. at 777. By “demanding a close fit between ends and means, the tailoring requirement prevents the government from too readily sacrificing speech for efficiency.” McCullen, 573 U.S. at 486.

Assuming there was some “evidence of traffic problems” caused by expressive horn use in some circumstances, the majority decision conflicts with this Court’s precedent by upholding a total ban, because courts “cannot simply assume” that expression causes problems in all circumstances. Comite de Jornaleros, 657 F.3d at 949 (holding ordinance banning curbside speech was not narrowly tailored to locations where hazards actually existed).

Any ban on expressive speech has to be narrowly tailored so as not to sweep protected speech within its ambit. The Ninth Circuit panel, with Judge Edward Korman from Brooklyn sitting by designation, wasn’t buying.

There is nothing novel about Section 27001’s traffic-safety justification—in fact, it seems the California legislature had traffic safety in mind when it first enacted a version of Section 27001 in 1913. That early version of the law prohibited honking “for any purpose except as a warning of danger.” . The traffic-safety justification for restricting the use of the horn can also be seen in the vehicle codes of at least forty other states, indicating a near-nationwide consensus on the need for such laws. This long history and consensus, coupled with the common-sense inference that the horn’s usefulness as a warning tool will decrease the more drivers use it for any other function, support the State’s asserted interest in traffic safety.

As the panel noted, the prohibition against horn honking was content neutral. Whether it was to indicate support for or against, it was prohibited. In this respect, it was akin to a time, place and manner limitation on expression. You can protest all you want, but you can’t do so on a public highway and prevent others from using the road for its intended purpose. So people can surely express their views, just not with a horn which the law provides is limited to warning of danger.

Honking is one of those very common practices that most of us do “unlawfully” at one time or another. See a friend? Honk. See a really cool 1964 Healey? Honk. Some jerk is doing 47 in the left lane of an interstate? Honk, honk, honk. Support bong hits 4 Jesus? Honk. When you’re driving in a car, how else would you express yourself? And yet, it hardly seems unreasonable for a law to prohibit use of a horn except as a warning of danger so as not to water down its utility.

Granted, it’s exceptionally rare for anyone to be cited for improper horn honking. Indeed, Porter’s citation was dismissed, but would she have been cited at all but for the protest she was supporting? By using the ban as a means to prohibit conduct due to its message, in this case support for a protest, it was unconstitutional as applied. But the case also presented the opportunity to challenge the constitutionality of the law itself.

The ubiquity of horn use as a means of expression seems to bolster the argument that the prohibition is overbroad. As argued, there are many instances where someone beeps where there is no question that it’s for a purpose other than warning of danger. And yet, the intended purpose of the law, to limit honking to warnings, hardly seems unreasonable and likely can’t be any more narrowly tailored without rendering the law incoherent. Is there any way to limit the ban to only situations where it would confuse other drivers as to whether the honking was intended to show support rather than warn? But is it really enough of a problem that it warrants a law prohibiting the use of horns as a means of expression?