This study provides ex post evidence on the retail price, consumption, and supply chain effects of animal confinement legislation (ACL), specifically California's Proposition 12, which prohibits the sale of pork from breeding sows housed below minimum space requirements. Using Circana weekly retail scanner data from January 2020 to January 2026 and USDA Livestock Mandatory Reporting (LMR) wholesale data from January 2022 through January 2026, we estimate regulatory effects by exploiting variation across the ACL-compliant and conventional pork markets. Following full ACL enforcement in January 2024, retail pork price premiums widened by 72.7 cents per pound in California and 62.8 cents per pound in Massachusetts, with an overall widening of 71.2 cents per pound. California's national pork purchase share declined from 8.5 to 7.1 percent. At the wholesale level, the ACL compliance premium averaged 24.2 cents per pound, and at the retail level, it was amplified by a factor of 2.95. The combined retail consumer cost for California and Massachusetts totals approximately $403.1 million over the enforcement period, with retail amplification accounting for the largest share (54.1%), followed by producer-received premiums (30.2%) and packer net margin (15.7%).
