Clutching UN security council documents, Salman Bashir said: "There are legal questions that arise in terms of the UN charter. Everyone ought to be mindful of their international obligations."
His comments, at a press conference in Islamabad, may have been aimed as much at preventing India from launching a unilateral raid on Pakistan territory in revenge for the 2008 Mumbai massacres as reproaching Washington.
Bashir added that this "violation of sovereignty, and the modalities for combating terrorism, raises certain legal and moral issues which fall ... in the domain of the international community".
As more detailed accounts of the assault on Bin Laden's compound in Abbottabad by US special forces emerged, international lawyers, religious leaders and human rights groups called for clearer justification of the legitimacy of the raid.
In London, the Archbishop of Canterbury, Dr Rowan Williams, said American confirmation that the al-Qaida leader was not holding a weapon when he died was disturbing. "The killing of an unarmed man is always going to leave a very uncomfortable feeling because it doesn't look as if justice is seen to be done," he said. "When we are faced with someone who was manifestly a war criminal in terms of the atrocities inflicted it is important that justice is seen to be served."
In the wake of reports that only one of those who died opened fire on the US Navy Seals team, repeated revisions of the initial, official version of events have reinforced international unease.
The veteran Cuban leader, Fidel Castro, was among those who exploited those doubts. The US president, he wrote, "has no way to hide that Osama was executed in the presence of his children and wives".
Following years of targeted killings by US drones along the Afghan/Pakistan border and in Yemen, the death of Bin Laden plays into a climate of legal and political suspicion about the lawfulness of American overseas strikes.
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The International Committee of the Red Cross discussed the Bin Laden case in Geneva. "The ICC do not ... have enough facts to assess the legal and humanitarian implications," a spokesman said.
Earlier this week, the UN's independent investigator on extrajudicial killings, Christof Heyns, said there was "considerable dispute in legal circles as to whether we are dealing with an armed conflict in respect of al-Qaida in Pakistan". Prof Nick Grief, an international lawyer at Kent University, said that the attack had the appearance of an "extrajudicial killing without due process of the law". He added: "It may not have been possible to take him alive... but no one should be outside the protection of the law." Even after the end of the second world war, Nazi war criminals had been given a fair trial, Grief added.
Comparisons between Bin Laden and Nazi war criminals have set the context for debates over whether greater effort should have been made to capture the founder of al-Qaida alive and bring him to justice in an international court.
The writer Toby Young said that a different second world war analogy applied, since al-Qaida had not surrendered, unlike the Nazis in 1945. Comparisons should not be with Nazi war trials, he wrote, "but with the plot to assassinate Hitler ... Had the Allies succeeded in assassinating any of the Nazi leaders during the Second World War, we would have applauded those responsible."
Most legal opinion in the United States has accepted the White House's rationale that the US is at war with al-Qaida. Steven Ratner, a professor at the University of Michigan law school, said: "A lot of it depends on whether you believe Osama bin Laden is a combatant in a war or a suspect in a mass murder."
If Bin Laden was a combatant, then "whether he has a gun or not really doesn't matter", Ratner said. "You're lawfully permitted to kill combatants." The US administration has asserted that he had two weapons within reach.
But David Scheffer, of Northwestern University school of law, pointed out that Bin Laden was indicted in Manhattan US district court in 1998 for conspiracy to attack US defence installations. "Normally when an individual is under indictment, the purpose is to capture that person to bring him to court to try him," Scheffer said. "The object is not to summarily execute him if he's under indictment."
Such questions may only be resolved if the instructions given to the US navy Seals are published and clarification given about what efforts were made force Bin Laden to surrender.