That said, I feel that it should be a rule that you have to warn your opponent if you're revoking permission to do that
But the thing is, you never have permission to take a missed opportunity unless the other guy expressly allows it. So it's not like someone actually revokes permission, rather they are no longer giving permission, and it should never be assumed you have permission in the first place.
Edit: That said... I do think you should let the other person know upfront if there is any sort of three strikes policy you're following, or if you'll allow missed opportunities the whole game.
That said I do think what PGS was a prime example of the WAAC attitude.
Edited by VanorDM