The euphoric chanting crowds at Ground Zero didn’t care, but the death of the world’s most wanted man Osama bin Laden raises a series of legal questions about the lawfulness of the assault.

Was it an assassination? Was bin Laden a “combatant” if he was living in relative peace in a country the United States is not at war with and was unarmed when killed?

Just three days after the haunting images of a smouldering New York skyline, the US Congress passed joint resolutions S.J.Res. 23 and H.J.Res. 64. These authorised the president to “use all necessary and appropriate force against those nations, organisations or persons he determines planned, authorised, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored such organisations or persons, in order to prevent any future acts of international terrorism against the United States by such nations, organisations or persons”.

But there are still questions over whether these resolutions allowed the specific assassination of those involved in the 9/11 attacks. Congress released a CRS (Congressional Research Service) Report — last updated on January 4, 2002 — explaining the legal ramifications of Executive Order 12333. It’s this executive order that banned assassination in the 1970s, after it was revealed the US had been involved in a number of questionable assassinations and assassination attempts on foreign leaders.

The terms “assassination” or “political assassination” were never clearly defined by the three presidents — Gerald Ford, Ronald Reagan and Jimmy Carter — involved in the Executive Order 12333 legislation, although the original intention of the law focused on foreign leaders.

The element of surprise — which was obviously integral to the killing of Osama bin Laden — is also raised as an issue on the legality of defining whether a killing is an “assassination” or a lawful killing.

However, the president may modify the assassination ban by executive order. Considering that Obama was watching live as bin Laden was shot in the left eye and killed, one could assume the executive order had been made if legally required.

The New Yorker raised how risky it was to suddenly allow political killings: “It is, to put it mildly, an easy power to abuse. bin Laden didn’t get a trial and didn’t deserve one. But the number of people for whom that is true is small. At least it should be.”

But Donald Rothwell, professor of international law at the ANU College of Law, regards bin Laden as a combatant to the US and says therefore his death was a lawful killing, not an assassination. He acknowledges others may differ on calling bin Laden a combatant.

“As a combatant he is therefore a lawful target and can be killed because he enjoys no immunity as a combatant,” explained Rothwell. “He has combatant status as he is the head of al-Qaeda, an organisation involved in armed conflict with the US, not only because of the events of 9/11 but because it continues to be at conflict with the United States.”

If bin Laden had been captured, rather than killed, the US would have become entangled in a plethora of legal issues, Rothwell said: “If he had been taken alive, issues would have been raised about would he have been subject to prosecution? Would it be before the US courts? Would he have been taken to Guantanamo? It clearly would raise a whole series of legal issues, ultimately not that dissimilar confronted with many of these people who have captured in recent years and taken to Guantanamo.”

The CRS report admits US Army manuals say that putting a price on the head of an enemy can turn a killing into an assassination as it encourages treachery from those nearest the enemy, although there was a US $25 million bounty on his head.

Rothwell agrees: “I think it does raise issues as to whether it ultimately encourages unlawful activities,” noting that there was no evidence to suggest the US$25 million reward helped find bin Laden.

“Perhaps the reward was more symbolic and reflects the Wild West culture that is sometimes associated with the United States.”