I contacted Honeyville, the ingredient supplier for Legacy Premium, to inquire about their non GMO claim:
http://legacyfoodstorage.com/honeyville-verifies-non-gmo-gluten-free-claims
The link above from Legacy states that Honeyville is the sole ingredient supplier and certifies their ingredients non GMO. However, when I contacted Honeyville to inquire about this certification the customer service rep said they have passed on my question to Legacy and will get back to me when they receive a response. The Honeyville rep was considerate enough so I'm willing to give them the benefit of the doubt and wait for their response.