An unwanted dog can be taken to the local animal control facility, a humane society or a rescue. If originally obtained from a breeder, the dog can often be returned to the breeder.
Because government-run animal control facilities are often overcrowded, animals that are surrendered by their owners are at high risk of euthanasia. Humane societies and no-kill shelters often accept unwanted dogs although many have waiting lists. Unwanted purebred dogs are often accepted by rescues specific to that particular breed.
Many breeders have policies in place that permit the return of a dog of their breeding at any time and for any reason. In addition, many rescues and humane societies have stipulations in their adoption contracts that require the adopter to return the dog to them if the adopter can no longer keep it.