Craig Keefe was expelled from his state-funded nursing college in Minnesota because something he said was deemed unprofessional. He didn’t break any laws with what he said—there were no threats or anything like that—and wasn’t even on campus at the time. He just made a handful of rude comments on his personal Facebook page, unrelated to any curricular project.

Nevertheless, the school had adopted the American Nurses Association’s code of professional ethics, which forbids behavior “unbecoming of the profession” or that “transgresses personal boundaries,” into its student handbook, so the federal district court rejected Keefe’s challenge to his expulsion. The U.S. Court of Appeals for the Eighth Circuit affirmed that ruling, effectively holding that that any punishment of speech under the nursing code is effectively free from First Amendment review.

So now Mr. Keefe, represented by Cato adjunct scholar Robert Corn-Revere, is asking the Supreme Court to take his case. Cato, joined by the Electronic Frontier Foundation, National Coalition Against Censorship, and Student Press Law Center, and with the help of Prof. Eugene Volokh and the UCLA First Amendment Clinic, has filed a brief supporting that request.

First Amendment protection is critical at universities, where complicated and controversial ideas are supposed to be formulated and debated. If uncorrected, the Eighth Circuit opinion permitting Keefe’s expulsion will set a dangerous precedent: Colleges will be able to punish students for expressing their views, based simply on administrators’ judgments that certain speech is inconsistent with their subjective understanding of professionalism.

Many professional-ethics codes—including the one at issue here—embody specific ideological commitments that might not be shared by large numbers of students, while also containing vague requirements that members uphold those values in their daily lives. The Eighth Circuit has opened the door for professional schools, including law and business schools, to enforce ideological litmus tests under the guise of ensuring adherence to professional ethics. Indeed, we have already seen—in cases the lower court cites to defend its position—students being targeted for their beliefs (for example, Keeton v. Anderson-Wiley (11th Cir. 2011), where a student was disciplined for statements disapproving of homosexuality).

Allowing viewpoint discrimination by way of professional codes of conduct opens up a gigantic loophole in the First Amendment’s freedom of speech, and in constitutional protections for conscience rights more broadly.

The Supreme Court will decide before it breaks for the summer at the end of June whether to take Keefe v. Adams.