The plaintiffs say the "shelter has a duty to help, not harm, homeless dogs and cats."
The Animal Legal Defense Fund along with three people from Stockton filed the lawsuit against the City of Stockton.
The suit is not asking for money, only that the animal shelter follow the law.
The shelter is required to hold strays for at least 6 days before euthanization.
But Animal Legal Defense Fund Attorney Jenni James says the shelter's records show a different story over a one year period.
"Early euthansias are happening, 1,500 animals were euthanized before the expiration of the Stockton shelter's minimum holding period," says James.
James says 80 percent of the animals are behind locked doors where the public never sees them.
"Only about 20 percent of the animals are truly being given a meaningful chance of adoption," says James.
The City of Stockton is not commenting on the lawsuit.
Hundreds of people visited the San Joaquin County Fairgrounds in Stockton on Thursday for the annual "Farm to Fork" event.
Tight water restrictions and increased conservation mean many California lawns are turning brown. But in Stockton, a landscaping company is making sure that the grass is always greener at some residents' homes.
(AP) - An attorney representing relatives of a bank robbery hostage who was shot and killed in Stockton says the family has agreed to an undisclosed financial settlement with Bank of the West.
(AP) - A measure expected to qualify for the November 2016 ballot could threaten Gov. Jerry Brown's $15 billion twin tunnel plan to send water around the Sacramento-San Joaquin Delta.
If you're a tennis fan, you can see some of the best young women players in the world this week at the $50,000 Pro Circuit Challenger in Stockton. Some players are looking for a comeback, others for a chance to play in the U.S. Open next month.