Federal law requires breeders that sell puppies wholesale or for research to obtain a federal license, but the Humane Society's study found that many ignore the requirement.
About half of states require no licensing or regulation of dog-breeding operations.
The Humane Society hopes that Virginia will consider limiting the number of puppies bred and sold by breeders each year.
Such legislation worries Bob Kane, president of the Virginia Hunting Dog Owners' Assn. Many houndsmen have numerous dogs, and Kane said he feared they would be swept up in the rush to pass laws aimed at unscrupulous puppy mills.
He especially worries about measures seeking to let inspectors from nonprofits like the Humane Society to go onto private property to evaluate animals' living conditions. (Such a provision was thrown out of a federal farm bill.)
"If they're not taking care of their dogs, regardless of how many there are . . . then I've got no use for them," Kane said. "I don't think private citizens ought to be the ones deciding this kind of thing."
