Article 49 of the Geneva Conventions prohibits ethnic cleansing:

Individual or mass forcible transfers, as well as deportations of protected persons from occupied territory to the territory of the Occupying Power or to that of any other country, occupied or not, are prohibited, regardless of their motive.

Any coerced transfer of Palestinians to the Sinai or Jordan or wherever would be a prima facie violation of this statute.

I know the response from many would be, "war crimes aren't real," and as much as I disagree with that viewpoint, let's set it aside. The real significance here is that if the United States and Israel openly commit ethnic cleansing, that act would be the official abandonment of the postwar moral consensus that has ruled the institutions of the First World for almost 80 years. The secular religion of the United States defines Hitler as Satan and the Geneva Conventions as its commandments. To flout those commandments would be publicly discarding the standard that makes Hitler into Satan.

Yes, US proxies have violated the Geneva Conventions several times and gotten away with it if they were valuable enough. But the fallout of this decision would be far bigger than that. Popes have gotten away with all kinds of degeneracy and graft behind the scenes, but a Pope has never publicly broken the commandments against adultery or theft and told everyone to just get over it.

The natural response would be, "well if you can get away with it, how come Satan can't?" And the emperor has no clothes.