Hm, this is a good discussion for this.
For me it all depends. League, ya ill let them take it back and explain to them that they can use the spray, but i would still be able to use my power again.
Premiere events, If im playing against a seasoned player, then no dice, because I know that they know how to play the game. If it was against a newer player, I would inform them of the same thing I would tell them at a league event.
StoG yes, but having fun doesnt mean you cant learn anything, and if it takes a mistake to learn, then thats what has to happen. Hopefully it only will happen once for that player.
~Duke