Illegal puppy farmers could take to shooting unwanted breeding dogs ahead of a potential new ban, animal rights campaigners have warned.
The Welsh Government has announced a consultation on so-called Lucy's Law.
It would ban dealers and pet shops from selling dogs and cats under six months old meaning they could only be obtained from licensed breeders or shelters.
One campaigner said she was already taking dogs off puppy farmers' hands after promising them anonymity.
A consultation in England ended in September while Wales' Rural Affairs Secretary Lesley Griffiths has said a similar consultation would begin in Wales early next year.
Linda Goodman, of dog welfare campaign Cariad, said she feared for the future for some breeding dogs: "They're in such poor shape they won't want to hand them over - they'll just shoot them," she said.
She hopes at least some of the illegal breeders will clean up and turn legitimate but fears councils will not have the budget to implement Lucy's Law.
"The councils know they cannot afford to police these new rules," she claimed, adding the public would "become the enforcement officers".
Eileen Jones, founder of Friends of Animals Wales, said she was already feeling the impact of Lucy's Law and up to twice a week was driving her van westwards from Pontypridd for clandestine meetings with illegal dog breeders.
They meet, often in secluded rural lay-bys, where the breeder hands over the once-caged dogs that then go on to a network of more than 50 fosterers to be domestically trained so they can be rehomed.
Her latest run was to meet an illegal breeder north of Llandeilo in Carmarthenshire where she picked up six Yorkshire Terrier breeding bitches, a Bichon and three Scottish Terriers.
She said over the past 13 years she has picked up thousands of redundant dogs.
Her phone number is passed around breeders and at farmers' markets as she is seen as an easy way to dispose of unwanted dogs. She says calls are "increasing drastically".
"Lucy's Law is already making a difference," she said.
"Lots of farmers are giving up, otherwise they're going to be stuck with puppies they can't sell."
Current legislation, which came into force in Wales in April 2015, requires anyone with three or more breeding bitches to be licensed by their local authority.
Figures provided to BBC Wales by 14 local councils show a total of 97 licensed breeders in those areas ranging from 33 in Ceredigion to none in Blaenau Gwent.
But Ms Jones puts the number of unlicensed puppy farms at ten times that number.
She said she was expecting more and more calls from puppy farmers and was focussing her efforts on finding more foster families to care for the redundant dogs.