California animal laws are some of the most progressive state animal laws in the country. They go beyond the reach of federal animal laws, so when researching animal law in California (as with any state), it is important to consider both the state laws and federal laws, as they are both at play.
Penal Code 597 is California's main animal welfare law. It makes it a crime to maliciously kill, harm, maim, or torture an animal, and violation is punishable by up to three years in prison, if charged as a felony. Public access to the law is linked above, but it can also be found on Lexis and Westlaw.
There are several other sections in the penal code that regulate more specific aspects of animal cruelty including failure to care for animals, live animal markets, animal fighting exhibitions, and transportation for slaughter. These provisions can be found by browsing Title 14 (Malicious Mischief) of the Penal Code at the same links as above.
California voters passed Proposition 12 in 2018, which sets stricter regulations on animal welfare for farmed animals. It sets minimum standards, like how much space animals must have when they are being bred in confinements. It is especially pertinent to the pork industry because hardly any pork farms in the country comply with these new standards, so some worry that pork will be very hard to get in Califoria. The related regulations have not yet been codified, but the California Department of Food & Agriculture (CDFA) has the proposed regulations on their website here, which would be added to Title 3 of the California Code of Regulations (CCR).
The USDA has compiled a page for State and Local laws related to animal welfare, with several different categories of laws. That list can be found here.
The Animal Legal Defense Fund (ALDF) has comprised a ranking of the "best" to "worst" states in the realm of animal protection laws. There is an accompanying report with more explanation and detail. That page can be found here.