San Francisco bans signage advertising “off-premises” activity, but not “on-premises” advertising. That is, if you own a liquor store, you can advertise the beers you have for sale, but not the upcoming beer festival you’re sponsoring across town.

But advertising is a form of speech protected by the First Amendment, and if the government wants to places limits on that speech, it must adhere to the constitutional limits on its own power. A company called Contest Promotions has challenged this law. The U.S. Court of Appeals for the Ninth Circuit ruled in the city’s favor, so now the company asks the Supreme Court to take its case.

At the core of the First Amendment is a principle of non-discrimination. That is, the government can place certain limits on speech in public places, but it may not preference some speakers over others based on the speech’s content or viewpoint. The content-based distinction San Francisco makes is precisely the sort of discrimination the constitution doesn’t abide. Unfortunately, the Supreme Court has made something of a muddle in this area. In Central Hudson v. Public Service Commission (1980), it set forth a special test for what is “commercial” speech, such as advertising, which it deemed less protected than other speech. It did this presumably to be able to better police fraud—which isn’t protected regardless—but that led to an unworkable standard and a litigation mess that lower courts have been unable to clean up.

Cato has now joined the Pacific Legal Foundation to file a brief in support of Contest Promotions, urging the Court to take up the case and reconsider its blunder in Central Hudson. The Court should dispense with a bifurcated First Amendment and treat commercial speech as on par with all other forms of expression. Moreover, it should clarify the boundaries of what does and doesn’t pass muster as a content-based restriction. Such distinctions require the most rigorous review (what lawyers call “strict scrutiny”), and the government should not be able to dodge the constitutional limits on their power by appealing to vague distinctions like “commercial” versus “noncommercial” speech.

The Supreme Court should put Contest Promotions v. San Francisco front an center on its docket in big, neon letters, and put an end to the jurisprudential murkiness in this area once and for all.