The international community has not accepted that reasoning, but it is an interesting exercise to figure out exactly how the world - specifically, the UN - has looked at Judea and Samaria over the years.
When did the territory become "Palestinian?"
When Israel regained that land in 1967, nobody referred to it and Gaza as "Palestinian territories."
The media sometimes called it "Israeli-occupied Jordan." But practically no one in the world accepted Jordan's annexation of the territory in 1950, and the UN certainly didn't.
UN resolutions in the 1970s referred to "Occupied Arab Territories" but that was because they were including the Sinai and Golan Heights which no one considers to be "Palestinian." Often the documents punted on the idea of exactly whose territories were being occupied by saying "Occupied West Bank."
One might think that the date that they became "Occupied Palestinian Territories," which the UN still refers to routinely as the "oPt." would be the date that Jordan formally gave up its claims on Judea and Samaria in 1988 and recognized the PLO as the sovereign of the territory. Even though Jordan itself had no legal right over the territory, perhaps that was the fig leaf that the UN used?
However, the UN started referring to the west bank of the Jordan as "occupied Palestinian territory" years before. The earliest I can find is from the report of an international conference on the question of Palestine in 1983, which refers to "occupied Palestinian and other Arab territories." (I found an earlier reference to the phrase in 1981 but it was from a speech by a Jordanian delegate to the UN and not from an official UN document.)
Also interestingly, the UN archive system seems to have changed the titles of some documents to refer to the "situation in the OPT" as early as 1979, but the documents themselves use no such language. Perhaps the UN archivist is trying to retroactively change history, but I'm not sure why they might have chosen 1979 as the start date.
If one does not accept Israel's argument from international law from San Remo, then there must be a date that the territories transferred to become "Palestinian." Transfer of territory is a legal matter that requires a legal transaction, whether it is a war or an agreement or an annexation. For those who do not accept Israel's claim, there is great confusion as to who legally owned the territory after the Ottoman Empire collapsed - was it the British? The League of Nations? And then, after 1948, was it Jordan?
But besides the Palestinians themselves, no one said that the territory was Palestinian - until the 1980s when the idea gained currency.
I still can't find that magic moment when the UN and the international community collectively decided that the land belonged to the PLO terror group, or to a people who nobody recognized as a people before the 1950s.
This indicates that the purported Palestinian ownership of the land has been more propaganda than law.