Well I'm not ashamed to say Pepsi came from a petshop/pet supplies place. they lady tht sold him to us was very thorough in her job, spent quite some time talking to us about him and our house and if we have got a good sized hutch, advising us and letting us hold him to see how he behaves and showing us the correct way to handle and pick him up. She then wrote everything we needed to know on the side of the box carrier (so we didn't loose little bits of paper), including when he should be introduced to veg, how to do it, the need for constant fresh hay, vaccinations, castrations and after 4 weeks of having him the shop gives you a free check up at the local vets.
Also, the vets come to the shop every week and check over each animal and check their welfare. They must have some contract but if it means people take them, the vets can see how the rabbit has been treated.
IMO if a breeder wont sell to someone then they will just go to another breeder and lie or go to a petshop and lie. It's something you just cannot police sadly. You can do a home check, but who is to say that the bunny will always be well kept once the novelty wears off or the owners circumstances change?
Instead of discouraging people from buying from certain places, perhaps they should be educated about keeping pets as I know that we did not expect half of what we have had to do for Pepsi until we went to the shop.
as much as I would love mind control 
