I think the primary way to stop puppy mills is if you want a dog "shop" your local shelter first. If you want a particular breed "shop" your local breed-specific rescue group first.

I can understand the need for respectable breeders and those working for the betterment of a breed especially for working dogs like guide dogs etc. You can find a great dog through a shelter or rescue group and you're saving a life.

Folks there are too many dogs and not enough good loving homes.