California Code, Food and Agricultural Code (Formerly Agricultural Code) - FAC § 52305

A farmer shall not be liable based on the presence or possession of a patented genetically engineered plant on real property owned or occupied by the farmer when the farmer did not knowingly buy or otherwise knowingly acquire the genetically engineered plant, the farmer acted in good faith and without knowledge of the genetically engineered nature of the plant, and when the genetically engineered plant is detected at a de minimis level. The authority of a court to determine the presence of de minimis levels of a genetically engineered plant is intended solely for the purpose of assisting in adjudicating claims relating to the possession or use of a patented genetically engineered plant in which the seed labeler, patentholder, or licensee, has rights. Nothing in this section is intended to do any of the following: