Prior to discovering free dining, we carried entire buffets (well, sort of) into the parks and as long as no glass containers were involved - no problem. It is wise to be aware of park policies wherever you go. (this is me preaching to the choir) If the CM or employee is wrong - stand your ground and request a supervisor.
My DD is at Seaworld,SA right now and they allow you to bring individual snacks, juice boxes, water and open drinks into the park, but not meals. Makes sense.
Which reminds me...I get to stop at EOS on the way home from San Antonio. WooHoo!