if they'd leave on their own it wouldn't be a problem. The land shown to Moses by God was promised to the Jews, the decendents of Jacob, not to Arabs. Arabs have way more land elsewhere, outside of Jewland. Besides, it isn't about all Arabs in the West Bank, only those who are there illegally. There's a difference.
from the article: Fayyad: New IDF orders threaten to empty West Bank of Palestinians