PUPS is important in order to make sure that all breeders of dogs have to be licensed with the USDA and comply with standards set forth by the Animal Welfare Act. Currently, the Animal Welfare Act and the USDA only inspect commercial breeders who sell their puppies to a wholesaler, for example a pet store. With the passage of PUPS, breeders who sell thier dogs remotely, to the public through the Internet, newspaper and telephone will have to become licesned under the USDA and follow humane standards set forth by the Animal Welfare Act. Such standards include health care, proper sanitation, excersie and cage specifications to name a few.
You can find more information about PUPS here:
Animal Welfare Act standards: http://www.aphis.usda.gov/animal_welfare/downloads/awr/awr.pdf