Last week’s UN report on war crimes committed during the Israeli invasion of Gaza leads to an inescapable conclusion: those behind the atrocities must be brought to justice. Yet despite lofty talk of global legal frameworks, the world is still a long way from realising the dream of an impartial legal system that can spring into action when evidence is presented that atrocities have been committed.

The investigation of Israeli’s actions in Gaza, led by the South African judge Richard Goldstone, found that Israel deliberately used “disproportionate force” during its three-week onslaught into Gaza, which ended in January. Although Palestinians bore the brunt of the casualties, with more than 1,400 killed, the probe also found that Hamas militants firing rockets into southern Israel had committed war crimes. Yet, Israel has already branded the 574- page report “one-sided” even as many impartial analysts have described the findings as an even-handed investigation carried out in a politically contentious arena.

While it criticises Palestinian militants, the report condemns Israel for committing war crimes and possibly crimes against humanity as the country’s military meted out collective punishment on the people of Gaza. This came as no surprise to Palestinian sympathisers in the Arab world and beyond, who were appalled by the destruction levied against the strip’s densely-packed population of 1.5 million.

Despite the clarity of his assessment, it was only after Mr Goldstone recommended action that the situation became muddied by questions over whether or how anyone would be tried for the crimes he documented.

The judge evidently wants his investigation to have teeth. He introduced his report in New York last week only metres from the doors of the UN Security Council, rather than in sleepy Geneva, where the investigation was first conceived.

Mr Goldstone criticised a “prolonged situation of impunity” and urged the 15-nation body to authorise an International Criminal Court (ICC) probe if Israel does not launch its own credible investigations within six months.

But, as has been shown repeatedly, this is easier said than done. Authorising such a referral requires approval from the council’s five permanent, veto-wielding members, including the US, which has traditionally offered unequivocal support to Israel.

Susan Rice, the US ambassador to the UN, dealt a blow to the report on Thursday, describing its origins as “unbalanced, one-sided and unacceptable”, saying that it should be handled by the toothless Human Rights Council in Geneva.

The UN secretary general Ban Ki-moon did little more than equivocate, telling journalists on the same day that “we will discuss this matter when we have fully reviewed the report”. Don’t hold your breath. Even Mr Ban’s own probe into UN facilities damaged during the Gaza onslaught was never acted upon by the Security Council.

Western publications have further dented the report’s credibility by claiming that it overlooked Israel’s efforts to minimise civilian deaths and the difficulties that all conventional militaries face when fighting guerrillas.

Still, delegates to the UN General Assembly, which convenes in New York today, will signal their support for the inquiry – or at least use its moral weight to bolster the Palestinian position during any future peace talks.

Rejecting Mr Goldstone’s conclusions out of hand, however, seems inconsistent with legal norms in any nation where the rule of law is enshrined. There, evidence of a crime is investigated and prosecuted until the accused is found to be either guilty or innocent.

But justice does not obey the same rules in the international arena. Here, the rule of law often comes as a secondary consideration to the political interests of great powers. The ultimate arbiter of international law is a 15-nation body that cemented the power of the US, Russia, China, France and the UK more than six decades ago.

While these may be the observations of the powerless, there is some consolation in the fact that the ICC, a war crimes tribunal in The Hague, is sharpening its teeth against alleged violators – even when such prosecutions remain controversial. Forged by 120 nations in 1998, the court has become bolder, issuing the world’s first arrest warrant against a sitting head of state, the Sudanese president Omar al Bashir, in March.

The court’s prosecutor, Luis Moreno-Ocampo, who achieved notoriety in the 1980s for trying military officers for atrocities in his native Argentina, appears set to launch more headline-grabbing prosecutions. Last week at UN headquarters, he told reporters he is collecting evidence of alleged violations committed by Nato troops and the Taliban in Afghanistan, as well as during Israel’s invasion of Gaza.

Mr Ocampo has often defended the court against allegations of being politically motivated, launching cases mostly against African militia leaders and being unwilling to tackle alleged atrocities authorised in Washington, Whitehall or the Kremlin. Now, the ICC prosecutor proudly proclaims that the era of impunity for all errant leaders is coming to an end, describing a “new line” of law that marks an “enormous evolution of the world”.

Perhaps without even realising it, Mr Ocampo used an American military ranking when describing to journalists his vision for how the laws of war must be respected by weak and powerful nations alike.

“Fifty years [in the future] we have a retired two-star general, sitting on the beach with his family when suddenly he is surrounded by policemen who handcuff him and go to the ICC,” he said. “That is the line. The world is defining a line: people cannot commit atrocities.”