Your question seems to be an extension of an urban myth that started back in 1999. Our cafeterias serve all types of food―including foods with ingredients from GM crops―every day. None of it is singled out as conventional or organic. It’s just food served in our cafeterias, the same food that everyone else eats.
I also want to make it clear that not only do our cafeterias serve foods made with GM ingredients, but they actually go out of their way on occasion to specifically source our genetically modified products. In fact, in August, we had a sweet-corn celebration that included serving our biotech/GM sweet corn in the cafeteria for a week and inviting a local farmer who grows that sweet corn on campus for a 1-day farmers' market. Our St. Louis-based employees were so excited to buy our biotech/GMO sweet corn that there were long lines and the farmer sold out of all of the corn that he brought.
We posted photos and a video from the event on our blog. You can read and view more here.
Regarding your question about bans, I am going to refer you to a very in-depth response to a similar question on GMO Answers: If GMOs are so great, why does Monsanto serve organic produce in it's cafeteria?