Can you provide any sources that show that someone can be jailed and/or fined? Case law or any codified law on the books that lays out what the charge would be or the fine/jail ranges associated with an offense of this nature? All I have ever seen is that the FDA has banned the main ingredient in Baytril for use in poultry, which they have done for many drugs. I have never seen any evidence of any sort of punishments for disobeying that ban though. Even the FDA press releases at the time of the ban do not mention any "teeth" behind it.
Yeah, the FDA has an enforcement arm, but they seem to focus solely on things like counterfeiting, theft, tampering, etc...
https://www.fda.gov/consumers/consumer-updates/fda-criminal-unit-guards-public-health
Guess what I mean is, have you ever come across any case law or press releases where the FDA came after anyone for "off label" use of a drug? I haven't. And they usually like to talk about that kind of stuff to scare others from doing it as well.