Once again, Hamas has launched a series of rocket attacks against Israeli civilian targets, including schools and kindergartens. Again, too, Israel has responded, as it must, with tactically suitable and law-enforcing retaliations. Nonetheless, and in predictably short order, the Palestinian side will surely allege a variety of Israeli violations, including the always manipulable charge of “disproportionality.”In this connection, unassailably, the fact that the rule of proportionality under the law of war has nothing to do with equivalence will be very conveniently swept under the rug.Significantly, recurrent Israeli resorts to force in Gaza are never gratuitous or contrived. Why should they be? Unlike their Hamas terrorist foes, Israelis deeply regret each and every resort to arms. Starkly unlike their bitterly recalcitrant enemies, Israelis receive no inherent joy from the organized killing of other human beings.In the presumptively endless Palestinian war against Israel, every sham is carefully glossed over with a shimmering patina. To begin, Hamas always takes calculated steps to ensure that Israeli reprisals will kill or injure Palestinian noncombatants. Again and again, by systematically placing elderly women and young children in exactly those same areas from which rockets are intentionally launched into Israeli homes, hospitals and schools, Hamas openly violates the most elementary expectations of the law of war.The almost ritualistic Hamas practice of “human shields” – the very same practice originally championed by Hezbollah in Lebanon – is more than an expression of “mere” immorality or cowardice. It also represents a very specific crime under international law. The technically correct name for this egregious crime is “perfidy.”Soon, Hamas will prepare for eventual mega-terror attacks on Israel. Such unprecedented attacks, possibly in cooperation with certain allied jihadist factions, both Palestinian and non-Palestinian, could include chemical and/or biological weapons of mass destruction. Over time, especially if Iran should agree to incrementally transfer certain portions of its hidden nuclear materials to terrorist groups, Israel could even face Hamas-directed nuclear terrorism. It is a threat that I have been lecturing and writing about for over 40 years. Such nuclear assaults against Israel could sometime be launched from trucks and ships, not only via rockets and missiles.Should Israel now negotiate more directly with Hamas to reduce these substantial risks? To what end? Hamas, after all, is still in the perpetual process of mending fences with the Palestinian Authority/Fatah, and neither of the two major Palestinian factions can speak authoritatively for other more-or-less murderous terrorist splinter groups.In essence, the core question here remains what it has always been: with whom should Israel negotiate? What government on earth could reasonably be expected to sit back passively and allow its unprotected population to face a still-preventable mass slaughter? Would we, in the United States, sit by quietly as rockets rained down upon American cities from terrorist sanctuaries – safe havens situated somewhere on our northern or southern borders? Could we imaginably ever allow such criminally- inflicted carnage to continue with impunity? Could capitulation and surrender ever be the proper or excusable reaction of a sovereign state that is implicitly sworn to protect its noncombatant populations? Although unrecognized and still unacknowledged, Israel has always sought to keep its essential counter-terrorism operations in Gaza consistent with humanitarian international law. Palestinian terror-violence, however, has remained in persistent violation of all civilized rules of engagement. All this, of course, has taken place after Israel very painfully “disengaged” from Gaza in 2005. That plainly hopeful departure of all Israelis from Gaza had been based on the presumption that the Palestinians would finally cease their apparently senseless and even self-destructive excursions into terrorism.Terrorism, anywhere, is always more than just bad behavior. Always, terrorism is a distinct and codified crime under international law. When terrorists represent populations that enthusiastically support such attacks, and where these terrorists can also find an easy refuge among hospitable populations, responsibility for ensuing counterterrorist harms must lie incontestably with the criminals.In law, truth can sometimes be counter-intuitive. Understood in terms of an inevitably still-ongoing cycle of Palestinian terrorism and Israeli self-defense, the Palestinian side must now bear full legal responsibility for Arab civilian casualties in Gaza. After all, without their premeditated attacks on Israeli civilian populations, there would have never been any Palestinian harms.Under international law, terrorists are Hostes humani generis, “Common enemies of humankind.” In law, such murderers must be punished severely wherever they are found. Concerning their arrest and prosecution, jurisdiction is now, after Nuremberg, “universal.”Deception can be legally acceptable in armed conflict, but the Hague Regulations disallow placement of military assets or personnel in heavily populated civilian areas. Further prohibition of perfidy is found at Protocol I of 1977, additional to the Geneva Conventions of 1949. It is widely recognized that these rules are also binding on the basis of customary international law.Perfidy represents an especially serious violation of the Law of War, one identified as a “grave breach” at Article 147 of Geneva Convention IV. The critical legal effect of perfidy committed by Palestinian terrorist leaders in Gaza has been to immunize Israel from any responsibility for unintended harms done to Arab civilians. Even if Hamas did not deliberately engage in perfidy, any Palestinian-created link between civilians and terrorist activities grants Israel full legal justification for initiating appropriately defensive military action.International law is not a suicide pact. All combatants, including Palestinian insurgents, are bound by the international laws of war. This requirement is found at Article 3, common to the four Geneva Conventions of August 12, 1949, and at the two protocols to these Conventions.Protocol I applies humanitarian international law to all conflicts fought for “self-determination,” the stated objective of all Palestinian fighters. A product of the Diplomatic Conference on the Reaffirmation and Development of International Humanitarian Law Applicable in Armed Conflicts (1977), this protocol brings all irregular forces within the full scope of international law. In this connection, the terms “fighter” and “irregular” are conspicuously inappropriate in describing Hamas terrorists, more-or-less fanatical criminals who “normally” target only civilians, and whose characteristic mode of “battle” is not military engagement, but religious sacrifice.In the final analysis, much of Hamas terrorism is rooted in a culture-wide search for immunity from personal death. It follows, unambiguously, that there can be no greater cowardice than is expressed by this particular form of terrorism. This generally neglected fact ought to be borne in mind worldwide during the coming weeks, when expected Hamas rocket attacks and random stabbings might wrongly be excused as “liberating,” and when indispensable military defense measures by Israel could wrongly be labeled as “disproportionate.”The author was educated at Princeton (PhD, 1971), and is the author of many books, monographs and articles dealing with terrorism and international law. Emeritus professor of international law at Purdue, his most recent writings can be found at The Bulletin of the Atomic Scientists; Harvard National Security Journal (Harvard Law School); International Security (Harvard); International Journal of Intelligence and Counterintelligence; Israel Journal of Foreign Affairs; Parameters, journal of the US Army War College; The Jerusalem Post; US News & World Report; The National Interest; The Hill; The Washington Times; The Atlantic; and Oxford University Press. His just published twelfth book is titled Surviving Amid Chaos: Israel’s Nuclear Strategy.