Before 1928, title to territory could be acquired by the use of force or through conquest. The 1928 Kellogg-Briand Pact, which created key principles of international law, brought about a change whereby the acquisition of territory by force was no longer lawful.
Self-determination: the Palestinian trump card - Opinion - Ahram Online
That could be why Israel has no land.
Didn't the Kellogg-Briand Pact outlaw war?