? about embargo

[PlayaFritz]

I was thinking about this move and wondered, in a battle with a real trainer, not in game, does this move prevent all of the foes items on all pokemon from being used, or just one?
I can't really figure out exactly how this move works?
If so, would it be useful in competetive play?

[Disintegration]

I think it's just the single Pokémon the move is used on. It refrains the effected Pokémon from using a held item and the Trainer from using an item on it. It doesn't sound very fair to effect all the opponent's team during the entire battle, unless it's temporary of course.