I’ve been covering this topic for several years at WhiskyCast, and have talked with the distillers at all three of the distilleries you mention in your piece about their reasons for using non-GMO corn. One of the key reasons they cite for using non-GMO corn is that they’re worried about health impacts that may not show up for many years. While that may not matter as much for companies making food products that are consumed immediately (compared to whiskey), when one has to mature a product for as long as 20 years or more before it’s ready to sell, there’s a legitimate reason to be concerned. If I have to wait 15 years before the whiskey I’m distilling today from GMO grain will be mature, and 14 years from now, scientists find out that there’s a major health risk from GMO grains, then that entire investment is screwed.
In addition, Wayne Parrott makes an excellent point. While US laws on GMO grain usage are quite liberal, the European Union and other countries are far more restrictive. If you’re going to export your product, it makes sense to produce it according to the most restrictive regulations you’re going to face to ensure compliance. However, it’s not correct to say that “many distilleries have been GMO-free for a long time.” I’ve asked every major whiskey distiller about their position on GMO’s, and Wild Turkey, Four Roses, and Buffalo Trace are the only ones who’ve come back and said they have policies against using GMO grains.