On Election Day, California voters will decide whether foods made from plants or animals with altered genetic material require mandatory labeling of this content. Some items — mainly organic foods, medical foods, restaurant foods, alcoholic beverages and foods made with only small amounts of GMOs — would be exempt under Proposition 37.

A former organic farmer from Chico, CA, launched the voter initiative, which picked up backing from organic food companies and alternative health advocates. Arguing against it are other food manufacturers, large and small, as well as chemical and seed companies. Similar laws have failed in 19 states, but as observers noted, California is different. Should Prop 37 pass, experts predict implementation delays and long, costly court fights.

Two University of California-Davis professors of agricultural economics estimated that Prop 37 could impose $2.7 billion on the state’s food processors in additional costs to meet segregation, monitoring and certification needs.