Tailgating at Iowa

I am traveling to Iowa City for the first time. We are tailgating at two separate spots and I am told by a local that beer and wine are the ONLY beverage that can be consumed. NO liquor of any kind at any tailgate. In addition, I am also told that if the authorities find liquor they will confiscate it, give you a ticket and possibly arrest you. Do I need to leave my Grey Goose martinis at home??? Anybody???