Meh, if they're still able to sell their dogs even with such a contract. All the power to them. I'd also question how easily that's enforceable. I'd never purchase a dog with that many restrictions on it, I'd actually never purchase a dog with ANY restrictions on it. It's way too easy to find a good breeder, producing amazing dogs, from titled parents, that doesn't have any restrictions on the dogs.
Remember, the care a breeder takes in vetting their potential customers doesn't say anything about the quality of their dogs or their breeding practices.