Soldiers cannot be criminally prosecuted simply for taking part in an armed conflict

John Walker Lindh's defence lawyers

Defence attorneys lodged documents on Monday, saying Mr Lindh could not be prosecuted simply for taking part in a conflict as a foot soldier.

They also challenged charges on the indictment that he supported the al-Qaeda network.

Mr Lindh, aged 21 and from California, was captured by US forces in Afghanistan last year when fighting for the Taleban against the Northern Alliance forces.

He faces 10 charges including conspiring to kill Americans and providing support to terrorists, including Osama Bin Laden's al-Qaeda.

International law

The defence team called on the US district court in Alexandria, Virginia, to dismiss the first count of conspiracy to commit murder.

Defence lawyers say Mr Lindh was tortured into confessing

"Soldiers cannot be criminally prosecuted simply for taking part in an armed conflict," the documents lodged by the lawyers said.

"There are no allegations or evidence that Mr Lindh committed any war crimes or otherwise violated the laws of war".

They also said that the US had previously used this point of international law to protest against the capture of its own soldiers abroad, for example the detention of US infantrymen in Kosovo.

In addition, the lawyers called for four other charges relating to Mr Lindh's alleged support for al-Qaeda and the Taleban to be dropped, saying that the legislation involved only covered financial or commercial help to the two organisations.

"The indictment does not specify what alleged actions by Mr Lindh the government believes constituted providing services to al-Qaeda and/or the Taleban," the lawyers say.

Defence protests

The team has previously protested against the conduct of the case, saying Mr Lindh had been "tortured" into confessing and was mistreated by the FBI on his arrest.

They revealed a photo to a US court, showing the terror suspect strapped naked to a stretcher and blindfolded.

They have also demanded access to prisoners held at the US base in Guantanamo Bay in Cuba.

The prosecution - whose case is largely built on his alleged confession - deny the claims of maltreatment.

Jury selection for the trial is due to begin in August, despite a plea by the defence to wait until after the first anniversary of the 11 September attacks.