For the first time since the establishment of Israel in 1948 the government is facing serious allegations of war crimes from respected public figures throughout the world. Even the secretary general of the United Nations, Ban Ki-moon, normally so cautious about offending sovereign states - especially those aligned with its most influential member, the United States - has joined the call for an investigation and potential accountability. To grasp the significance of these developments it is necessary to explain what made the 22 days of attacks in Gaza stand shockingly apart from the many prior recourses to force by Israel to uphold its security and strategic interests.

In my view, what made the Gaza attacks launched on 27 December different from the main wars fought by Israel over the years was that the weapons and tactics used devastated an essentially defenceless civilian population. The one-sidedness of the encounter was so stark, as signalled by the relative casualties on both sides (more than 100 to 1; 1300-plus Palestinians killed compared with 13 Israelis, and several of these by friendly fire), that most commentators refrained from attaching the label "war".

The Israelis and their friends talk of "retaliation" and "the right of Israel to defend itself". Critics described the attacks as a "massacre" or relied on the language of war crimes and crimes against humanity. In the past Israeli uses of force were often widely condemned, especially by Arab governments, including charges that the UN Charter was being violated, but there was an implicit acknowledgement that Israel was using force in a war mode. War crimes charges (to the extent they were made) came only from radical governments and the extreme left.

The early Israeli wars were fought against Arab neighbours which were quite literally challenging Israel's right to exist as a sovereign state. The outbreaks of force were of an inter-governmental nature; and even when Israel exhibited its military superiority in the June 1967 six day war, it was treated within the framework of normal world politics, and though it may have been unlawful, it was not criminal.

But from the 1982 Lebanon war this started to change. The main target then was the presence of the Palestine Liberation Organisation (PLO) in southern Lebanon. But the war is now mainly remembered for its ending, with the slaughter of hundreds of unarmed Palestinian civilians in the refugee camps of Sabra and Shatila. Although this atrocity was the work of a Lebanese Christian militia, Israeli acquiescence, control and complicity were clearly part of the picture. Still, this was an incident which, though alarming, was not the whole of the military operation, which Israel justified as necessary due to the Lebanese government's inability to prevent its territory from being used to threaten Israeli security.

The legacy of the 1982 war was Israeli occupation of southern Lebanon and the formation of Hizbullah in reaction, mounting an armed resistance that finally led to a shamefaced Israeli withdrawal in 1998. This set the stage for the 2006 Lebanon war in which the announced adversary was Hizbullah, and the combat zone inevitably merged portions of the Lebanese civilian population with the military campaign undertaken to destroy Hizbullah. Such a use of hi-tech Israeli force against Hizbullah raised the issue of fighting against a hostile society with no equivalent means of defending itself rather than against an enemy state. It also raised questions about whether reliance on a military option was even relevant to Israel's political goals, as Hizbullah emerged from the war stronger, and the only real result was to damage the reputation of the IDF as a fighting force and to leave southern Lebanon devastated.

The Gaza operation brought these concerns to the fore as it dramatised this shift away from fighting states to struggles against armed resistance movements, and with a related shift from the language of "war" to "criminality". In one important respect, Israel managed to skew perceptions and discourse by getting the media and diplomats to focus the basic international criminal law question on whether or not Israeli use of force was "disproportionate".

This way of describing Israeli recourse to force ignores the foundational issue: were the attacks in any legal sense "defensive" in character in the first place? An inquiry into the surrounding circumstances shows an absence of any kind of defensive necessity: a temporary ceasefire between Israel and Hamas that had been in effect since 19 July 2008 had succeeded in reducing cross-border violence virtually to zero; Hamas consistently offered to extend the ceasefire, even to a longer period of ten years; the breakdown of the ceasefire is not primarily the result of Hamas rocket fire, but came about mainly as a result of an Israeli air attack on 4 November that killed six Hamas fighters in Gaza.

Disproportionate force?

In other words, there were no grounds for claiming the right of self-defence as Israel was not the object of a Hamas attack, and diplomatic alternatives to force existed and seemed credible, and their good-faith reliance was legally obligatory. On this basis the focus of legal debate should not be upon whether Israeli force was disproportionate. Of course it was. The focus should be on whether the Israeli attacks were a prohibited, non-defensive use of force under the UN charter, amounting to an act of aggression, and as such constituting a crime against peace. At Nuremberg after the second world war, surviving Nazi leaders were charged with this crime, which was described in the judgment as "the supreme crime" encompassing the others.

The Gaza form of encounter almost by necessity blurs the line between war and crime, and when it occurs in a confined, densely populated area such as Gaza, necessarily intermingles the resistance fighters with the civilian population. It also induces the resistance effort to rely on criminal targeting of civilians as it has no military capacity directly to oppose state violence. In this respect, the Israeli attacks on Gaza and the Hamas resistance crossed the line between lawful combat and war crimes.

These two sides should not be viewed as equally responsible for the recent events. Israel initiated the Gaza campaign without adequate legal foundation or just cause, and was responsible for causing the overwhelming proportion of devastation and the entirety of civilian suffering. Israeli reliance on a military approach to defeat or punish Gaza was intrinsically "criminal", and as such demonstrative of both violations of the law of war and the commission of crimes against humanity.

There is another element that strengthens the allegation of aggression. The population of Gaza had been subjected to a punitive blockade for 18 months when Israel launched its attacks. This blockade was widely, and correctly, viewed as collective punishment in a form that violated Articles 33 and 55 of the Fourth Geneva Convention governing the conduct of an occupying power in relation to the civilian population living under occupation. This policy was itself condemned as a crime against humanity, as well as a grave breach of international humanitarian law.

It also had resulted in serious nutritional deficiencies and widespread mental disorders on the part of the entire Gaza population, leaving it particularly vulnerable to the sort of "shock and awe" attack mounted by Israel from land, air and sea. This vulnerability was reinforced by Israel's unwillingness to allow Gaza civilians to seek safety while the tiny Strip was under such intense combat pressure. Two hundred non-Palestinian wives were allowed to leave, which underscored the criminality of locking children, women, the sick, elderly and disabled into the war zone, and showed its ethnically discriminatory character. This appears to be the first time in wartime conditions that a civilian population was denied the possibility of becoming refugees.

In addition to these big picture issues, there are a variety of alleged war crimes associated with Israeli battlefield practices. These charges, based on evidence collected by human rights groups, include IDF firing at a variety of civilian targets, instances where Israeli military personnel denied medical aid to wounded Palestinians, and others where ambulances were prevented from reaching their destinations. There are also documented claims of 20 occasions on which Israeli soldiers were seen firing at women and children carrying white flags. And there are various allegations associated with the use of phosphorus bombs in residential areas of Gaza, as well as legal complaints about the use of a new cruel weapon, known as DIME, that explodes with such force that it rips body parts to pieces.

These war crimes concerns can only be resolved by factual clarifications as to whether a basis exists for possible prosecution of the perpetrators, and commanders and political leaders to the extent that criminal tactics and weaponry were authorised as matters of Israeli policy. In this vein too are the Israeli claims relating to rockets fired at civilian targets and to Hamas militants using "human shields" and deliberately attacking from non-military targets.

Even without further investigation, it is not too soon to raise questions about individual accountability for war crimes. The most serious allegations relate to the pre-existing blockade, the intrinsic criminality and non-defensiveness of the attack itself; and the official policies (eg confinement of civilian population in the war zone) have been acknowledged. The charges against Hamas require further investigation and legal assessment before it is appropriate to discuss possible arrangements for imposing accountability.

A question immediately arises as to whether talk of Israeli war crimes is nothing more than talk. Are there any prospects that the allegations will be followed up with effective procedures to establish accountability? There are a variety of potentially usable mechanisms to impose accountability, but will any of these be available in practice? This issue has been already raised by the Israeli government at the highest levels in the form of official commitments to shield Israeli soldiers from facing war crimes charges.

The most obvious path to address the broader questions of criminal accountability would be to invoke the jurisdiction of the International Criminal Court established in 2002. Although the prosecutor has been asked to investigate the possibility of such a proceeding, it is highly unlikely to lead anywhere since Israel is not a member and, by most assessments, Palestine is not yet a state or party to the statute of the ICC. Belatedly, and somewhat surprisingly, the Palestinian Authority sought, after the 19 January ceasefire, to adhere to the Rome Treaty establishing the ICC. But even if its membership is accepted, which is unlikely, the date of adherence would probably rule out legal action based on prior events such as the Gaza military operation. And it is certain that Israel would not cooperate with the ICC with respect to evidence, witnesses or defendants, and this would make it very difficult to proceed even if the other hurdles could be overcome.

The next most obvious possibility would be to follow the path chosen in the 1990s by the UN Security Council, establishing ad hoc international criminal tribunals, as was done to address the crimes associated with the break-up of former Yugoslavia and with the Rwanda massacres of 1994. This path seems blocked in relation to Israel as the US, and likely other European permanent members, would veto any such proposal. In theory, the General Assembly could exercise parallel authority, as human rights are within its purview and it is authorised by Article 22 of the UN charter to "establish such subsidiary organs as it deems necessary for the performance of its function". In 1950 it acted on this basis to establish the UN Administrative Tribunal, mandated to resolve employment disputes with UN staff members.

The geopolitical realities that exist within the UN make this an unlikely course of action (although it is under investigation). At present there does not seem to be sufficient inter-governmental political will to embark on such a controversial path, but civil society pressure may yet make this a plausible option, especially if Israel persists in maintaining its criminally unlawful blockade of Gaza, resisting widespread calls, including by President Obama, to open the crossings from Israel. Even in the unlikely event that it is established, such a tribunal could not function effectively without a high degree of cooperation with the government of the country whose leaders and soldiers are being accused. Unlike former Yugoslavia and Rwanda, Israel's political leadership would certainly do its best to obstruct the activities of any international body charged with prosecuting Israeli war crimes.

Claims of universal jurisdiction

Perhaps the most plausible governmental path would be reliance on claims of universal jurisdiction (1) associated with the authority of national courts to prosecute certain categories of war crimes, depending on national legislation. Such legislation exists in varying forms in more than 12 countries, including Spain, Belgium, France, Germany, Britain and the US. Spain has already indicted several leading Israeli military officers, although there is political pressure on the Spanish government to alter its criminal law to disallow such an undertaking in the absence of those accused.

This path to criminal accountability was taken in 1998 when a Spanish high court indicted the former Chilean dictator, Augusto Pinochet, and he was later detained in Britain where the legal duty to extradite was finally upheld on rather narrow grounds by a majority of the Law Lords, the highest court in the country. Pinochet was not extradited however, but returned to Chile on grounds of unfitness to stand trial, and died in Chile while criminal proceedings against him were under way.

Whether universal jurisdiction provides a practical means of responding to the war crimes charges arising out of the Gaza experience is doubtful. National procedures are likely to be swayed by political pressures, as were German courts, which a year ago declined to proceed against Donald Rumsfeld on torture charges despite a strong evidentiary basis and the near certainty that he would not be prosecuted in the US, which as his home state had the legally acknowledged prior jurisdictional claim. Also, universal jurisdictional proceedings are quite random, depending on either the cooperation of other governments by way of extradition or the happenchance of finding a potential defendant within the territory of the prosecuting state.

It is possible that a high profile proceeding could occur, and this would give great attention to the war crimes issue, and so universal jurisdiction is probably the most promising approach to Israeli accountability despite formidable obstacles. Even if no conviction results (and none exists for comparable allegations), the mere threat of detention and possible prosecution is likely to inhibit the travel plans of individuals likely to be detained on war crime charges; and has some political relevance with respect to the international reputation of a government.

There is, of course, the theoretical possibility that prosecutions, at least for battlefield practices such as shooting surrendering civilians, would be undertaken in Israeli criminal courts. Respected Israeli human rights organisations, including B'Tselem, are gathering evidence for such legal actions and advance the argument that an Israeli initiative has the national benefit of undermining the international calls for legal action.

This Israeli initiative, even if nothing follows in the way of legal action, as seems almost certain due to political constraints, has significance. It will lend credence to the controversial international contentions that criminal indictment and prosecution of Israeli political and military leaders and war crimes perpetrators should take place in some legal venue. If politics blocks legal action in Israel, then the implementation of international criminal law depends on taking whatever action is possible in either an international tribunal or foreign national courts, and if this proves impossible, then by convening a non-governmental civil society tribunal with symbolic legal authority.

What seems reasonably clear is that despite the clamour for war crimes investigations and accountability, the political will is lacking to proceed against Israel at the inter-governmental level, whether within the UN or outside. The realities of geopolitics are built around double standards when it comes to war crimes. It is one thing to proceed against Saddam Hussein or Slobodan Milosevic, but quite another to go against George W Bush or Ehud Olmert. Ever since the Nuremberg trials after the second world war, there exists impunity for those who act on behalf of powerful, undefeated states and nothing is likely to challenge this fact of international life in the near future, thus tarnishing the status of international law as a vehicle for global justice that is consistent in its enforcement efforts. When it comes to international criminal law, there continues to exist impunity for the strong and victorious, and potential accountability for the weak or defeated.

It does seem likely that civil society initiatives will lead to the establishment of one or more tribunals operating without the benefit of governmental authorisation. Such tribunals became prominent in the Vietnam war when Bertrand Russell took the lead in establishing the Russell Tribunal. Since then the Permanent Peoples Tribunal based in Rome has organised more than 20 sessions on a variety of international topics that neither the UN nor governments will touch.

In 2005 the World Tribunal on Iraq, held in Istanbul, heard evidence from 54 witnesses, and its jury, presided over by the Indian novelist Arundhati Roy, issued a Declaration of Conscience that condemned the US and Britain for the invasion and occupation of Iraq, and named names of leaders in both countries who should be held criminally accountable.

The tribunal compiled an impressive documentary record as to criminal charges, and received considerable media attention, at least in the Middle East. Such an undertaking is attacked or ignored by the media because it is one-sided, and lacking in legal weight, but in the absence of formal action on accountability, such informal initiatives fill a legal vacuum, at least symbolically, and give legitimacy to non-violent anti-war undertakings.

The legitimacy war

In the end, the haunting question is whether the war crimes concerns raised by Israel's behaviour in Gaza matters, and if so, how. I believe it matters greatly in what might be called "the second war" - the legitimacy war that often ends up shaping the political outcome more than battlefield results. The US won every battle in the Vietnam war and lost the war; the same with France in Indochina and Algeria, and the Soviet Union in Afghanistan. The Shah of Iran collapsed, as did the apartheid regime in South Africa, because of defeats in the legitimacy war.

It is my view that this surfacing of criminal charges against Israel during and after its attacks on Gaza resulted in major gains on the legitimacy front for the Palestinians. The widespread popular perceptions of Israeli criminality, especially the sense of waging war against a defenceless population with modern weaponry, has prompted people around the world to propose boycotts, divestments and sanctions. This mobilisation exerts pressure on governments and corporations to desist from relations with Israel, and is reminiscent of the worldwide anti-apartheid campaign that did so much to alter the political landscape in South Africa. Winning the legitimacy war is no guarantee that Palestinian self-determination will be achieved in the coming years. But it does change the political equation in ways that are not fully discernable at this time.

The global setup provides a legal framework capable of imposing international criminal law, but it will not be implemented unless the political will is present. Israel is likely to be insulated from formal judicial initiatives addressing war crimes charges, but will face the fallout arising from the credibility that these charges possess for world public opinion. This fallout is reshaping the underlying Israel/Palestine struggle, and giving far greater salience to the legitimacy war (fought on a global political battlefield) than was previously the case.