There's some rule that if it isn't a dark soda/pop (like Coca-Cola or Pepsi) that it can't have caffeine unless it calls it an energy drink. You can get Mt Dew with caffeine in it (and it's called an energy drink) I believe... but it's not the standard pop you can get anywhere. *shrug*

http://en.wikipedia.org/wiki/Mountain_Dew

it says it there