When Wayne Hsiung and other animal rights activists entered Sunrise Farms, a giant egg facility in Petaluma, on May 29, 2018, to provide aid to suffering chickens, they thought their right to rescue these birds would be protected from criminal liability by California’s “necessity defense,” which justifies breaking the law to prevent a “significant evil.” The necessity defense helps to ensure that people do not hesitate to intervene to prevent harm out of fear that they will be prosecuted for...