Opinion of the Court
07/a-brief-for-the-pigs-the-case-of-national-pork-producerscouncil-v-ross/. These animals may receive their only opportunity for exercise when they are moved to a separate barn to give birth and later returned for another 16 weeks of pregnancy confinement—with the cycle repeating until the pigs are slaughtered. Ibid. Proponents hoped that Proposition 12 would go a long way toward eliminating pork sourced in this manner “from the California marketplace.” A. Padilla, Cal. Secretary of State, California General Election—Official Voter Information Guide 70 (Nov. 6, 2018) (Voter Guide), https://vig.cdn.sos.ca.gov/2018/general/pdf/complete-vig.pdf. Proponents also suggested that the law would have health benefits for consumers because “packing animals in tiny, filthy cages increases the risk of food poisoning.” Ibid.; see App. to Pet. for Cert. 201a–202a.
Opponents pressed their case in strong terms too. They argued that existing farming practices did a better job of protecting animal welfare (for example, by preventing pig-on-pig aggression) and ensuring consumer health (by avoiding contamination) than Proposition 12 would. Id., at 185a–187a; see also Voter Guide 70–71. They also warned voters that Proposition 12 would require some farmers and processors to incur new costs. Id., at 69. Ones that might be “passed through” to California consumers. Ibid.
Shortly after Proposition 12’s adoption, two organizations—the National Pork Producers Council and the American Farm Bureau Federation (collectively, petitioners)—filed this lawsuit on behalf of their members who raise and process pigs. App. to Pet. for Cert. 154a–155a. Petitioners alleged that Proposition 12 violates the U. S. Constitution by impermissibly burdening interstate commerce. Id., at 230a–232a.
In support of that legal claim, petitioners pleaded a number of facts. They acknowledged that, in response to consumer demand and the laws of other States, 28% of their
