How long has the United States been at war...?

A US military war tribunal in the Guantanamo Bay concentration camp on Cuba is weighing a question that might seem better suited for a history class than a courtroom - how long has the United States been at war?

But the question is more than academic for Abd al-Rahim al-Nashiri, whose lawyers are appearing before the tribunal this week to seek the dismissal of war crimes charges approved by a Pentagon-appointed legal official.

Nashiri faces trial in a special tribunal for wartime offences known as a military commission.

He's charged with orchestrating the bombing of the USS Cole in Yemen in 2000 as well as attacks on two other ships.

But his lawyers are illustrating one of the fundamental problems of the US system of military kangaroo courts.

They say that since the US wasn't at war at that time, the 47-year-old shouldn't be tried at Guantanamo.

"The fact of going to war is a decision by the political branches, either Congress or the president or both," defence lawyer Richard Kammen said on Monday.

"It's not something to be arrived at retroactively by a bureaucrat who is not appointed by Congress, because it has huge consequences."

Nashiri's lawyers say that the US wasn't at war until after the September 11 2001 attacks and then president George W Bush did not certify the existence of hostilities of any kind in Yemen until September 2003.

The motion for dismissal is one of 21 matters set for consideration in a hearing that started on Tuesday at the base, where the US holds 166 prisoners, most of whom have not been charged with any crime.

The hearing is scheduled to run through until tomorrow.

Other items on this week's agenda include whether Nashiri should be forced to attend the hearings and whether the US government should turn over information about a man killed in a US drone strike in Yemen in 2002 who was identified in some media reports as the mastermind of the Cole attack.

"If he was killed based on the fact that he was the mastermind behind the USS Cole that's relevant," said Navy Lieutenant Commander Stephen Reyes, his military lawyer.

Nashiri, who was born in Saudi Arabia to a Yemeni father and a Saudi mother, has been held at Guantanamo since September 2006.

An allegedly senior member of al-Qaida, he was held for four years in the secret CIA network of overseas prisons, where he was subjected to the "enhanced" interrogation programme that included at least two instances of waterboarding.

The government has admitted that he was also threatened with a gun and a power drill because interrogators believed he was withholding information about possible attacks against the US.

In November he was arraigned on charges that included terrorism and murder for the attack on the USS Cole, which killed 17 sailors and wounded 37, as well as for orchestrating the October 2002 bombing of the French tanker MV Limburg, which killed one crewman and a failed January 2000 plot on the USS The Sullivans.

He faces the death penalty at a trial that his lawyers say is at least a year away.

In making the case for the military tribunal, prosecutors lay out the history of what they claim was al-Qaida's escalating war against the US, starting with an August 1996 declaration by Osama bin Laden calling for the murder of US personnel serving on the Arabian peninsula.

However it wasn't until a week after the September 11 2001 terrorist attacks that Congress and president Bush approved an authorisation for military force.

And Nashiri's lawyers say that former president Bill Clinton repeatedly said that the country was at peace in the aftermath of the Cole attack.

A group of retired admirals and generals who served as senior military legal officials have called for the military charges to be dismissed and for the case to be shifted to a civilian criminal court.

In a brief in October as part of a civil challenge to the case, they also argued that the definition of war was being improperly expanded to include non-war offences in the Nashiri case and that such a use of the military courts could put US soldiers and citizens in jeopardy in the future if other countries did the same thing to them.

"If countries can retroactively decide we were at war and chuck people from the civilian court systems into prisoner of war systems with the attendant lack of protections, that road runs both ways," Kammen said.

"Once you get to go back in time and rewrite history that's a very, very dangerous precedent."