Proposition 12 sets animal confinement legislation (ACL) that pork must meet to be sold in California. Because the rule applies at the point of sale, its effects run through the entire supply chain, from the farm and packing plant to the retail shelf. Using weekly Circana retail scanner data and Livestock Mandatory Reporting (LMR) data, this brief examines the retail and wholesale impacts of Proposition 12 and estimates compliance costs along the supply chain. At retail, the California price gap relative to the rest of the United States widened sharply after full enforcement and has remained elevated for two full years, with cut-level premiums rising by 14 to 32 percentage points. California's share of total U.S. pork volume declined from 8.5% to 7.1%, with the largest drop in ribs. Sausage, an exempt benchmark, showed no change in its price premium. At wholesale, ACL-compliant pork accounted for an average of 5.3% of reported volume and traded at a compliance-attributable premium of 24.2 cents per pound, indicating that compliant and conventional pork coexist as parallel wholesale channels rather than a market converging on full compliance. Applied to observed volumes from January 2024 to January 2026, these premiums imply an estimated economic burden of $184.7 million at wholesale and $403.1 million at retail in California and Massachusetts combined. Producers received $121.6 million in compliance premiums, packers retained $63.1 million in net margin, and the remaining $218.4 million reflects retail amplification. The retail price effect was therefore nearly three times the wholesale compliance premium, indicating that the largest economic effects emerged between the packing plant and the retail shelf.
