According to the international law it is 1949's borders. This is the borders that were set after the first humiliating military defeat of the arabs against Israel. Remember? But it is actually more complicated because all territory on the west bank beyond this border is not Palestinian. It is considered by the international community "disputed" territory.
One student killed, three wounded at Arizona campus during fight (a)
from the article: Dividing the Land of Israel into two states is a moral imperative