Some states require that any animal being shipped be checked out by a veterinarian and given a written bill of good health less than two weeks prior to the actual shipping. The specifics, or even if this is actually required or not, varies from state-to-state.

A lot of big breeders state on their websites that prices include health certificates if the buyer's state requires it. I've personally never gotten health certificates for animals before shipping (I live in Tennessee) but I've likewise never had a buyer say they require it.

So whether or not people actually abide by this law is a totally different story.