Once formally established, a state of Palestine would quickly become a staging area for expanding conflict and terror against Israel. This is hardly a secret. At the same time, Hezbollah would increase its own rocket operations against Israel from Lebanon.The threat of violence would force Israel to undertake defensive operations. Any resultant noncombatant deaths in all relevant theaters of conflict would, of course, elicit howls of international condemnation. There would again be claims made against Israel for alleged violations of international law. The loudest allegations of all, assuredly, would predictably be sanctimonious cries of "disproportionality."The law of war requires that every use of force by an army or insurgent group meet the test of "proportionality." Proportionality stipulates that every resort to armed force must be limited to what is absolutely necessary for meeting essential military objectives. This principle applies to all calculations of military advantage — and to all reprisals.Louis René Beres is Professor of International Law at Purdue University. He is a frequent contributor to The Jerusalem Post.Proportionality does not mean that the defending state must limit its use of force to the precise amount used by the other side. Here, the conventional wisdom is flat out wrong. This is not a judgment of equivalent destructiveness. These legal decisions may also take into proper account the extent to which an adversary has committed prior, or even ongoing violations of humanitarian international law. Under international law, deception can be acceptable in armed conflict, but the Hague Regulations do not permit the placement of military assets or military personnel in populated civilian areas. Prohibition of perfidy can be found at Protocol I of 1977, an addition to the Geneva Convention of 1949. These rules are further reinforced by customary international law.Perfidy represents a very serious violation of the law of war. It is even identified as a “grave breach” in Article 147 of Geneva Convention No. IV. The legal effect of perfidy committed by Palestinian or Hezbollah terrorists has been to exclude Israel from any legal responsibility for counter-terrorist harms done to Arab civilians. Historically, viewed against the background of extensive and always unapologetic terrorist perfidy in Palestinian territories and Lebanon, Israel has been innocent of any disproportionality. All combatants, including all insurgents, are bound to comply with the law of war of international law. This firm requirement derives not only from what is known as the “Martens Clause,” a paragraph that makes its first appearance in the Preamble to the 1899 Hague Convention No. II on land warfare, but additionally, from Article 3, common to the four Geneva Conventions of August 12, 1949. It is also found at the two Protocols to these Conventions. Any seemingly disproportionate uses of force by Israel have actually been the permissible outcome of prior crimes committed by its enemies. What about Lebanon and the charge of "aggression?" It is not possible for Israel to commit such a crime. Lebanon considers itself in a formal condition of belligerency with the Jewish State. A state cannot commit aggression against another state with which it is already at war.The central legal issue in Middle East conflict is not about Israeli disproportionality or aggression but rather a persistent Arab willingness to resort to terrorism and perfidy. Soon, the UN could again take up the issue of membership for "Palestine." Although any such consideration would not likely meet the stringent requirements of statehood that were established at the 1934 Convention on the Rights and Duties of States (Montevideo Convention), a generally-recognized and totally militarized Palestinian state would then become a reality. Israel's more unstable future would then depend on Article 12 of the PA (Fatah) Charter, which calls for "the liberation of Palestine completely....," and at Article 19: "The struggle will not end until the elimination of the Zionist entity and the liberation of Palestine." As for the "less-moderate" Hamas Covenant (Charter of the Islamic Resistance Movement), it begins with Israel's annihilation: "Israel will exist and will continue to exist until Islam will obliterate it."International law is not a suicide pact. It stipulates, quite precisely, that a beleaguered state can do what is required to protect itself against the grave harms of terrorism and war. As long as Israel remains consciously committed to the legally correct meanings of proportionality and does whatever is possible to minimize the collateral harms of its essential defensive force, Jerusalem need not concern itself about the always contrived charges of IDF wrongdoing.For the jurisprudential record, moreover, Israel remains the only state in the Middle East that has stayed impressively true to the law of war, and to its own "purity of arms."