What if the government of Palestine were somehow willing to consider itself bound by its pre-state, non-treaty agreement? Even in these very improbable circumstances, the new Arab administration would retain ample grounds for lawful treaty termination.
More precisely, a new Palestinian government could withdraw from the agreement because of what it would regard as a "material breach," that is, a reputed violation by Israel that had allegedly undermined the object or purpose of the agreement. It could also point toward what Latinized international law calls Rebus sic stantibus. In English, this relevant doctrine is known more clearly as a "fundamental change of circumstances."
If Palestine should declare itself vulnerable to unforeseen dangers, perhaps even from the interventionary or prospectively occupying forces of certain other Arab armies, it could lawfully end its previously-codified commitment to remain demilitarized.
Still another factor explains why Netanyahu's apparent hopes for Palestinian demilitarization are ill-founded. After declaring independence, any new Palestinian government could point to pre-independence errors of fact, or to duress, as appropriate grounds for agreement termination. Here, the usual grounds that may be invoked under ordinary domestic law to invalidate contracts could also be applied to treaties, or to treaty-like agreements.
Any treaty is void if, at the time of entry into force, it is in conflict with a "peremptory" rule of international law. This is a norm accepted by the community of states as one from which "no derogation is permitted." Because the right of sovereign states to maintain national military forces for self-defense is always such a rule, Palestine could be entirely within its lawful right to abrogate any agreement that had previously, before independence, compelled its demilitarization.
Netanyahu should take no comfort from any legal promises of Palestinian demilitarization. Should the government of any future Palestinian state choose to invite foreign armies or terrorists on to its territory, possibly after the original government had been overthrown by even more militantly Jihadist or Islamic forces, it could do so not only without practical difficulties, but also without violating international law.
The core danger to Israel of any promised Palestinian demilitarization is always more geopolitical than legal. The U.S.-driven Road Map stems from a consistently basic misunderstanding of Palestinian history and goals. At a minimum, Obama should finally recall that the Palestine Liberation Organization as formed in 1964. Significantly, this was three years before there were any "occupied territories."
What, then, were the Palestinians seeking to "liberate?" The answer, of course, was and still remains, all of Israel.
Louis Rene Beres is a professor of International Law at Purdue University. Born in Zurich, Switzerland at the end of World War II, he is the author of many major books and articles dealing with world politics, law, literature and philosophy.