The 3 province rule really needs to be inspected regarding these kinds of actions.
Austria: "Separate" war, 2 provinces
Venice: "Separate" war, 2 provinces
Portugal: Joined England/Holland and managed to tie up the majority of the spanish army with the help of venetian/english/danish relief armies. Thus when we win, I will have no way of forcing him to give back the 2 provinces concerned in the deal we made a couple of sessions back which he subsequently broke.
I'm going to have to go ahead and disagree with the current system, and it will REALLY need reworking for Machiavelli 3.