Last Tuesday, Prime Minister Benjamin Netanyahu announced his intention to immediately annex the West Bank’s Jordan Valley after Israel’s election on Sept. 17, should he emerge victorious. He further pledged to apply sovereignty to Israel’s settlements throughout the West Bank after President Trump unveils his Israeli-Palestinian peace initiative.

But Mr. Netanyahu’s fortunes and Mr. Trump’s plan may not matter. Under the radar, the Israelis and Palestinians have already set ominous precedents in administering their divided territories that will be extremely difficult to back away from and promise an incendiary environment for any talks about a lasting peace.

In short, the longstanding rules of temporary side-by-side coexistence in the West Bank, as set out under the Oslo Accords in the 1990s, are already being violated, and bit by bit both sides are taking steps that would nullify the remaining vestiges of the accords. If that trend continues, what is shaping events on the ground now may render any type of future division impossible.

Here is the problem: Oslo created clear lines of administrative control in the West Bank for Israel and the Palestinians by dividing the territory into distinct zones in which each side is responsible for day-to-day governing. Areas A and B are under Palestinian Authority administrative control, and Area C is under Israeli administrative control. While there have been numerous and continuing violations by both sides when it comes to security responsibility, that has not been the case with administrative responsibility. Until recently, Israel exercised its administrative control of Area C without attempting to extend its administrative reach into Areas A and B, while the Palestinian Authority ran Areas A and B with respect for Israel’s monopoly on governing Area C.