Nearly 40 years ago, the Supreme Court held in Wooley v. Maynard (1977)—the famous “Live Free or Die” case from New Hampshire—that the First Amendment protects against being compelled to convey a message displayed on a state-issued license plate. Nevertheless, the Denver-based U.S. Court of Appeals for the Tenth Circuit recently held that someone could not object to an image on Oklahoma’s license plate of the Sacred Rain Arrow statue, which depicts a young Apache warrior shooting an arrow into the sky as a prayer for rain.

The court’s decision turned on drawing a line between speech in the form of words and other kinds of expression. Keith Cressman had objected to the Oklahoma tag because of the history and origin of the Sacred Rain Arrow statue. The Tenth Circuit held that Cressman’s objection was not entitled to full First Amendment protection because images are not “pure speech” and must be analyzed under the less rigorous “symbolic speech” test.

The term “symbolic speech” may be an unfortunate misnomer—it doesn’t mean speech via symbols—but the Supreme Court has only ever used the phrase to refer to “expressive conduct.” That is, “symbolic speech” is conduct that conveys a message, such as burning one’s draft card in protest of war.

The Supreme Court has always regarded non-conduct forms of expression as “pure speech.” And that’s exactly as it should be: Government has no more ability to ban bumper stickers displaying a cross than ones referencing “John 3:16,” and the same must be true for ones depicting Da Vinci’s painting “The Last Supper.” Despite the Court’s consistency on this point, lower courts are split. While the Ninth Circuit has extended full First Amendment protection to tattoos and even the process of making them and the business of tattooing, other circuits have suggested that “pure speech” is limited to words. And of course the Tenth Circuit has now said that the First Amendment protects as symbolic speech at best.

But the Tenth Circuit’s ruling did even more harm to the First Amendment than that, because the court also held that, regardless of what kind of speech the image was, the First Amendment didn’t support Cressman because he didn’t object to the actual message Oklahoma was sending; his understanding of the image didn’t align with the state’s. That holding is particularly problematic when the speech at issue is visual art, which is inherently open to interpretation and has no authoritative interpretation.

Consider, for example, Cloud Gate—better known as the Chicago Bean—whose sculptor sought to convey themes of immateriality, spirituality, and the tension between the masculine and the feminine. But most people who take selfies in front of the Bean have no idea what it’s meant to convey, or might think it has to do with distorted reflection and the like. The freedom of speech—even the freedom to think—would be threatened if compelled-speech cases hinged on whether plaintiffs “really” disagreed with the “actual” message the government was sending and thus could be compelled to speak because they opposed it for their own “wrong” reasons.

In the quintessential compelled-speech case, West Virginia State Board of Education v. Barnette (1943), the Supreme Court held that the First Amendment protected Jehovah’s Witnesses having to salute the American flag and recite the Pledge of Allegiance. Surely the Constitution would have likewise protected an atheist who opposed the flag salute because the stars represent the heavens and man’s divine goal—even though most people today don’t know that history.

But the Tenth Circuit’s decision said otherwise: The First Amendment would have protected Cressman if he objected to Oklahoma’s Native American message but did not protect him when his objection was based on what it considered to be a misunderstanding about the Sacred Rain Arrow statue. As in religious-freedom cases, courts shouldn’t evaluate the reasons behind an objection to compelled speech.

Mr. Cressman has asked the Supreme Court to review his case, and Cato has filed an amicus brief making the above arguments in support of that petition.