What's wrong with this sentence?...  

I read this and blinked:

The U.S. Food and Drug Administration prohibited some unapproved uses of antibiotics in livestock on Wednesday.

Farmers will no longer be able to administer a class of antibiotics called cephalosporins to cattle, pigs, chicken and turkeys in unapproved doses or frequencies, or as a means of preventing disease, the agency said. [More]

I assumed I understood what "unapproved" meant, but maybe not.

That has long been a concern of many public health experts, including the Pew Health Group. Pew said in a press release today that while "the FDA has approved cephalosporins to treat some infections in food animals, the drugs often are administered in ways not specifically approved by the agency."
This "extralabel" use of antibiotics by livestock producers is linked to the emergence of resistant bacteria, or superbugs, that have infected tens of thousands of people, according to David Wallinga, a physician at the Institute for Agriculture and Trade Policy and a member of the Keep Antibiotics Working coalition.
Today, the FDA said the drugs remain critically important for humans, so their use should be restricted only to humans.
The decision to restrict the cephalosporins comes just two weeks after the FDA announced it was trashing a 1977 proposal to remove approvals for two antibiotics, penicillins and tetracyclines, used in livestock and poultry feed.
An association of veterinarians says the new rule on cephalosporins won't have a big impact. They can still use these other antibiotics to keep animals healthy. [More]

How can off-label use not be prohibited? 

So, is this just the FDA, saying "We really mean it this time!"?