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.
Seven candidates are vying to be Stockton's next mayor -- one of them held that same position more than 50 years ago.
Proponents of a measure to allow four medical marijuana dispensaries in Stockton have turned in a petition with more than 8,500 signatures. That’s almost 3,000 more than what are needed to put the initiative before the voters.
Stockton Mayor Anthony Silva touched on finances, safety and the future during the 18th State of the City speech. The mayor addressed a packed house of about a thousand people.
Stockton Police and other law enforcement agencies made a major sweep of criminals and guns as the city faces a major rise in homicides and shootings in the city. More than 50 alleged gang members were taken off the street on Wednesday.
A rising number of homicides in Stockton is a cause for concern for police. So far this year, 17 people have been murdered. Last year at this time, there had been nine killings.