20 years,
Some states have passed such laws.
And there is a consensus as to the safety of GMO food. To suggest otherwise is to search for the very few antagonists who 'feel' differently. From Scientific American: "The American Association for the Advancement of Science, the World Health Organization and the exceptionally vigilant European Union agree that GMOs are just as safe as other foods. Compared with conventional breeding techniques—which swap giant chunks of DNA between one plant and another—genetic engineering is far more precise and, in most cases, is less likely to produce an unexpected result. The U.S. Food and Drug Administration has tested all the GMOs on the market to determine whether they are toxic or allergenic. They are not."
Based on meta-data studies, GMOs are safe, kinder to the environment and more profitable for farmers. Soon those few extremist reactionaries will be likened to Jenny McCarthy and her rants about vaccinations. Unless, of course, Killer Tomatoes terrorize the villagers.
Once again theists and non-theists are on essentially opposite sides of an OP, This occurs whether the topic is religious or secular. Feeling, Believing, Thinking, Knowing, Proving.