This of course raises the question, how far back in history is relevant?
You can always argue that "in year x the land was ours so we want it back" then the other side can say "but in the year x it was ours so we´re keeping it".
Then the real big problem of "were Gods people, God gave us this land" or similar derivations of this idea.
Maybe some alien race will come along one day and say "hey what are you cocroaches doing on our planet, which we built ages ago and left to grow, time to die."