Proposition 12, approved by more than 62% of the state’s voters in 2018, requires producers of breeding pigs to house them in cages of at least 24 square feet, allowing them enough room to turn around. It also set standards for cages that hold egg-laying hens and veal calves and banned the sale in California of meat — including pork, produced almost entirely in other states — from animals held in cages that violated those standards.