In January the state of North Carolina ordered Steve Cooksey to stop writing about how the “paleo” diet helped him cope with diabetes.

The paleo diet, which consists mostly of meat and fresh vegetables, is modeled after pre-agricultural eating patterns. Cooksey, a logistics manager for a medical supply company from Stanley, North Carolina, found that the diet controlled his blood sugar levels and helped him lose more than 75 pounds. He began a website, diabetes-warrior.net, to tell the world about the diet’s good effects on him. North Carolina’s Board of Dietetics/Nutrition ordered him to stop, sending him an edited version of the site’s content that it deemed acceptable. Even private email messages or calls discussing his diet experience were forbidden, he was told, unless he became a state-licensed dietician.

In May, with the help of the Institute for Justice, a libertarian public interest law firm based in Arlington, Virginia, Cooksey sued the board in federal court, claiming its attempt to censor his website violates his right to freedom of speech. The case touches on one of the great unresolved questions in First Amendment jurisprudence: When does occupational licensing trump free speech? The implications are potentially wide. Data from a 2010 study by economists Morris Kleiner of the University of Minnesota and Alan Krueger of Princeton indicate that occupational licenses are required for one in three American workers.