WASHINGTON – Veterinarians do not have a free speech right to give online advice to pet owners about how to care for a sick animal, said a decision that the Supreme Court let stand on Monday.

The justices turned down a First Amendment challenge to a Texas law that requires vets to examine an animal before offering advice or suggesting treatment.

The libertarian Institute for Justice contended such "occupational speech" restrictions often serve to prop up established professions and harm consumers who could benefit from advice at a low cost.

But repeatedly, the high court has deferred to state regulators who have used their licensing authority to enforce limits on professionals, including not just doctors and psychologists, but also tour guides and interior designers.

Dr. Ronald Hines, a semiretired veterinarian in Texas, sued to challenge the state law after he was fined for offering advice online. He had founded a website after his retirement and posted articles about ­caring for pets.

But when pet owners contacted him and asked for help with a sick animal, he began answering questions and offering advice. He charged a flat fee of $58 to those who could afford to pay.

He did not prescribe medication and sometimes recommended the owners take their pet for a physical examination. But in 2012, the Texas Board of Veterinary Medical Examiners accused him of violating state law by offering advice without having personally examined the animal.

The law specifically prohibited vets from interacting with animal owners "solely by telephone or electronic means." He was fined $500; he then sued, alleging the law violated his First Amendment rights. He won before a district judge, but lost before the Fifth Circuit Court of Appeals.

In a 3-0 decision, the judges said states have broad power to regulate professionals and that the Texas law imposes a particular standard of care — one that requires examining an animal in person. "It does not regulate the content of any speech or require veterinarians to deliver any particular message," they said.

Similar disputes have arisen in a variety of situations. Two years ago, the Ninth Circuit Court of Appeals rejected a First Amendment challenge to a California law that prohibited "conversion therapy" designed to change the sexual orientation of minors. The judges said this was a restriction on a medical treatment, not on advice or speech.

Meanwhile, judges on the Eleventh Circuit Court in Atlanta have issued conflicting opinions on a Florida law that prohibits doctors from asking patients about whether they keep firearms at home.

In the Hines case, the Institute for Justice appealed on the veterinarian's behalf and urged the high court to decide how far states may go to regulate the speech of professionals.