"FDA can inform, but it has identified no authority allowing it to recommend consumers 'stop' taking medicine,"  U.S. Circuit Judge Don Willett wrote in the ruling.

The FDA has authority under the Federal Food, Drug, and Cosmetic Act to convey information to consumers.

The FDA during the COVID-19 pandemic has issued multiple statements discouraging people from taking ivermectin against COVID-19.

Accompanied by a picture of a horse and a link to an FDA webpage on ivermectin, the agency wrote in one social media post: "You are not a horse. You are not a cow. Seriously, y'all. Stop it."

The page it linked to is titled, "Why You Should Not Use Ivermectin to Treat or Prevent COVID-19."

Three doctors sued the FDA over its statements on ivermectin, arguing the agency cannot advise doctors on which drugs to prescribe.

Ivermectin is approved by the agency as an antiparasitic drug for both humans and animals.

Federal law gives the government immunity against legal actions, with some exceptions. One exception, known as ultra vires, is when an official acts outside their authority. Plaintiffs challenging the acts must show that the official was "acting 'without any authority whatever,' or without any 'colorable basis for the exercise of authority,'" according to an earlier court ruling.

The FDA does have the authority to share data and facts, the parties agree. But they diverge on whether the FDA can issue recommendations on medical matters, such as treatments.

The FDA has claimed that the posts do not contain advice, stating in one brief that they were "informational statements" that "do not 'direct' consumers, or anyone else, to do or refrain from doing anything." At the same time, the FDA acknowledged that the statements "provided recommendations" and "advise[d] consumers."