Mexico City, Mexico - Pet owners, breeders and veterinarians in Mexico's capital are howling over a law passed by the city council requiring sterilization, chip implants, and registration of all cats and dogs.

Veterinarian and breeder groups published full-page newspaper ads Thursday saying the law could endanger thousands of jobs at clinics, pet salons, and breeding and training facilities by causing a sharp drop in pet numbers. The Mexican Dog Fanciers Federation said the law was rushed through in early May without adequate consultation.

The city of nearly 9 million people has a serious problem with strays, puppy mills, animal mistreatment, and illegal pet sales.

Over a few weeks in late 2012 and early 2013, at least five people were killed by what investigators said was a pack of dogs running loose in a park on Mexico City's east side.

But usually, dogs suffer more than humans from the lack of controls. Animal pounds and rescue shelters are inadequate, and many dogs lucky enough to have a home are confined to narrow balconies or small rooftops for much of the day.

The law, which is not yet formally enacted, would require owners to register pets, implant identification chips, use collars with ID tags, and provide animals with adequate food, water, and space.

Trainers could not work with pets in public. Pets would have to be leashed in public, while children under 14 wouldn't be allowed to walk pets alone.

Special permits will be needed to own "potentially dangerous" dogs, including pit bulls, mastiffs, and rottweilers. Those dogs would have to be muzzled and leashed in public.

The most controversial aspect is a requirement that all pets must be sterilized.

Legal breeders say that violates owners' rights to breed animals responsibly. Worse, they say, the law could force legitimate facilities out of business, leaving puppy and kitten breeding in the hands of unscrupulous dealers who sell animals out of car trunks or from crates at street markets.

"The decision to sterilize pets should be voluntary," said Juan Luis Martinez, administrative director of the Mexican Dog Fanciers Federation.

He said the law's requirements, including fines from about $100 up to as much as $5,000, could lead some poor residents to abandon pets in streets or parks.

"This could encourage noncompliance with the law, or lead people to dump them in the street," Martinez said.