That's dependant on the pokemon's level.
If one is level 40, I believe you would need 4 or 5 badges for it to obey you.
Anything higher is 6th badges? (Sabrina's badge) which makes them obey till level 70.
The Earth badge, which is the last, makes ALL obey you.

and if u trade pokemon back do they stop obeying u?

like i want to trade a kadabra over for it to evole than trade it back

Pokemon will always obey the Original trainer regardless of level.

okay alright ty =]

Havent really done anything yet, only gotten up to mistys gym, havent played much, been playing some other games, but since im going on a vacation soon, if theres no internet at the place im staying at ill just play pokemon =p

sounds like a great vacation !