Why is Tariq Aziz still being held captive?

Question to any 'humanitarian' interventionists who might be reading this.
Why, if Tariq Aziz, former Deputy Prime Minister of Iraq is not on trial and not being charged with anything- is he still being held in captivity by US forces? Is there a new offence of 'being a member of a government which doesn't do what the NWO tells it to do?'
http://www.guardian.co.uk/Iraq/Story/0,,1782079,00.html

UPDATE: Judging by Aziz's appearance in court today and the concerns about his deteriorating health from his family - it seems they're opting for the 'Slobo' option -i.e. we've got no evidence, so let's provoke a premature death. Here's The Jurist.

http://jurist.law.pitt.edu/paperchase/2006/01/
Friday, January 13, 2006
Lawyer says former Iraq deputy PM Aziz seriously ill Krystal MacIntyre at 11:05 AM ET

[JURIST] Former Iraqi Deputy Prime Minister Tariq Aziz [BBC profile] is ailing and may have only weeks to live, lawyer Badia Aref said Thursday, claiming his client is suffering from high blood pressure, cannot walk properly, and is being given 13 pills a day for heart problems, diabetes and other illnesses. Aziz was once the spokesman for the Saddam Hussein [JURIST news archive] government abroad in the 1980s and early 1990s and was jailed after the 2003 invasion of Iraq; HE IS STILL HELD IN SECLUSION EVEN THOUGH NO FORMAL CHARGES HAVE BEEN BROUGHT AGAINST HIM. A spokesman for the US military, which has physical custody over detained former senior members of Saddam's regime, said there had been no significant deterioration in Aziz's health, and that he was suffering from "existing ailments" at the time he was taken into custody.