This is interesting, as my daughter has been working Saturdays at a Farmers' Market in Washington DC. They get a lot of stuff from some Amish farms in PA, including eggs, heavy cream and raw milk. I asked her if there were any special requirements for selling the PA produce over a state line and she said .... if there is, that particular item is marked 'pet food only.' Now, everybody BUYS the stuff for more than pet food, but because he labels it as such, gets past regulation.
Not sure I agree with this, and was surprised how 'commonplace' my daughter said is was at the 'green' city markets.