In the Soprano universe,there was not a Commission to mediate disputes between Families. I always found this to be a little strange,especially given Chase's reliance on real life Mob examples for his storylines. If memory serves me,disputes that arose between the Sopranos and the Lupertazzis were settled by them on their own.

Had there been a Commission,Phil would have had to get their OK to hit Tony and his top guys. It would be interesting to see what rationalization he would have used to make a case for killing Tony.I can't think of anything that would have swayed a vote in Phil's favor.
Tony would not have needed approval to hit back ,since self defense is an accepted reason to act without having to wait for permission.