Well, Proposition 37, requiring labeling of GMO foods in California, was defeated by the overwhelming resources of self-interested corporations. Free markets mean all necessary information. By hiding the contents of their products, agribusinesses are denying free markets to the consumer. See "Letter about GMO foods".
You might also consider the words of Adam Smith in "Wealth of Nations":
"The proposal of any new law or regulation of commerce which comes from this order, ought always to be listened to with great precaution, and ought never to be adopted till after having been long and carefully examined, not only with the most scrupulous, but with the most suspicious attention. It comes from an order of men, whose interest is never exactly the same with that of the public, who have generally an interest to deceive and even to oppress the public, and who accordingly have, upon many occasions, both deceived and oppressed it." - pages 142-143
I included the above in "The Invisible Adam Smith".
I hope you're not allergic to any foods that have been spliced into other foods.
