Considering that attacking from outside is obviously participating actively in a turf war you should be allowed to kill anyone doing so. I don't think the "Either the attacker or the defender must be in the turf zone at the time of engaging" should be removed but reworded so it's clear you are not supposed to attack people who are on their way to the turf area but you are free to attack those who are already taking part actively (attacking already). Plus we don't get to face situations like in BC where people go walking to the turf and shoot eachother before even arriving to the zone, then cry.