There's something of a safeguard put up on the event Pokemon that will make them always disobey you, regardless of level, if you obtained them using an encounter code, or didn't properly activate the event for it.
Oh great. Is there any way to fix it?
EDIT: Yeah, I used encounter codes to get my Celebi, Mewtwo, and Deoyxs also. And they listen to me!
it's by warping to birth island/world's edge island and catching the deoxys/mew there.There is a certain way you can obtain via cheating that will make it listen. But I'm not sure what exactly that is.