Not exactly seeing how this is at all legalizing liberty(referring to your username). This would be the opposite in regards to liberty it is limiting what a farmer can do. The local farmers were largely in agreement, similar to healthcare providers enjoying Obamacare. Yes many industries to prefer more regulation. You bet a farmer doesn't want his competition to grow something that is more resistant to pests and drought as his is.
I am all for the market deciding to label GMO food, similar to organic food and they can reach their own standards. I also disagree with any sort of patent infringement lawsuits that companies go after for seed dispersal. But again making more things illegal is not helping liberty in anyway.