Washington, D.C. has served as the backdrop to some of the most important speeches in American history—from Martin Luther King’s “I Have a Dream,” to Franklin Roosevelt’s stirring call for a declaration of war after Pearl Harbor, to almost every president’s inaugural address (some less memorable than others). The city is also home to monuments and statutes celebrating the memory of men and women who spent their lives fighting for freedom, especially the freedom of speech.

But if you want to show this history off to tourists, you’d better have a license. District law requires tour guides to pass a history test on 14 subjects, covering material from no less than eight different publications, before they can go into business—all for the purpose of “protecting” tourists from misinformation.

In other words, you have to get a “speaking license” from the city.

Tonia Edwards and Bill Main operate “Segs in the City,” a company that gives Segway tours of the city’s historical landmarks, and they are unlicensed. Consistent with the history and values of free speech represented by D.C.’s monuments, the Institute for Justice is helping these entrepreneurs challenge the licensing law as an unconstitutional abridgment of First Amendment rights. After losing in district court, the plaintiffs appealed to the U.S. Court of Appeals for the D.C. Circuit.

Joined by First Amendment expert Eugene Volokh, Cato has filed an amicus brief supporting the lawsuit. We argue that the licensing regime is a content-based restraint on speech and therefore must pass the strictest judicial scrutiny (so the government needs a compelling reason for it and has no other way of accomplishing the same goal). The law is a content-based speech regulation in that it is (a) triggered by the content of speech, and (b) justified on the basis of the content that it regulates.

The Supreme Court has repeatedly held that a law regulating the content of speech — as opposed to its location, timing, or manner — is subject to strict scrutiny. The justifications offered for the licensing law explicitly refer to the content of guides’ speech (“misinformation”). That is as much a content-based justification as saying that people need to be protected from hearing “erroneous” political opinions or “controversial” historical theories.

Finally, we argue that tour guides are not members of a “profession,” such as lawyers, doctors, and accountants, which could merit less First Amendment protection in order to protect the public from harm. Unlike those professions, tour guides don’t have intimate relations with clients. Instead, like most businesses, they simply have customers. The government cannot possibly require authors, public lecturers, or documentary filmmakers to get licensed in order to protect the public from “misinformation,” and it has no more basis for licensing tour guides.