Definition of a "Natural" Body Building Show?

DBB'ers,
 
I'm thinking about entering a show, I know that natural means you can't take any steroids or any other "deemed" illegal products but is there any formal documentation re this?   Or is it different in every state or is this handled by each individual sponsor of the events?    Just looking for clarification on what supplements I can and can't take.   Don't want to be one of the many athletes who claim they were unaware of a supplement that had a banned substance in it.
 
Thanks for any input
 

Height 5' 8" Weight  200 lbs Body Fat 16%
Bench 315-Squat 365-Dead 405
Chest-46"/Bicep-16.5"/Waist-37"...UGGH
Thigh-24.5"/Calves 16"

    

I know a lot of events are different, they want it to be a natural show, but some events don't have the money to actually test the athletes. As long as you don't use anything illegal you will be fine. It depends what type of show you do, like for instance NPG shows are supposed to be all natural, but not everyone follows the rules, NPC is more of a mix I would say

Current Stack:
FOOD!!!
Opti-Men Multi
Universal Storm 
ON 100% Whey
Muscle Milk
Jacked Pre-Workout
Flax Oil