The law targets the controversial breeding facilities known as puppy mills or kitten factories, which often operate with little or no oversight and “house animals in overcrowded and unsanitary conditions without adequate food, water, socialization or veterinary care,” according to a fact sheet for the legislation, AB 485.

The new rules took effect Tuesday after Gov. Jerry Brown signed them into law in October 2017.

While some cities and counties in California already restricted sales from unlicensed breeding facilities, the law was the first to apply across the state, the fact sheet said. Pet store owners who do not comply face a penalty of $500 per animal.

“Because pet stores are one step removed from the breeding of the animals they sell, store owners rarely know the breeding conditions of their animals,” the fact sheet said.

People may still buy dogs or cats directly from breeders.

The statewide legislation is the first of its kind to take effect in the United States, but other states are following suit with similar regulations that affect pet retail outlets.

More than 250 cities and local governments across the country have similar measures that curtail mass breeding operations of dogs and cats, the ASPCA said. In November, Atlanta became the ninth city in Georgia to prohibit so-called puppy and kitten mills. Instead, pet stores would exclusively offer cats and dogs for adoption, the City Council announced.

In Maryland, Gov. Larry Hogan signed a law in April that bars pet store operators from selling dogs and cats but allows them to host adoptions. Stores may benefit financially from the adoptions because they can lure potential customers, O’Neill said.

The law in Maryland, which takes effect in 2020, has not put a damper on business at Charm City Puppies in Columbia, which has sold about 95 dogs in the past month, said Ashley Lawson, an assistant manager. She said Wednesday that the store sold only animals from federally licensed breeders across the United States.

“Today we are actually low on puppies because of the holiday season,” she said, although the store was selling a Cavalier King Charles spaniel for $2,499 and a Yorkshire terrier for $1,999.

This article originally appeared in The New York Times.