In the New Zealand news today, there is an article titled Kiwi troops in 'war crimes' row:
New Zealand stands accused of "war crimes" for handing over prisoners who were mistreated by the American military during George W Bush's so-called war against terror in Afghanistan.
International legal experts say New Zealand broke the Geneva Convention and laws against torture when, from 2002, [New Zealand's] elite SAS troops transferred 50-70 prisoners to the Americans at the Kandahar detention centre in southern Afghanistan.
Now I'm hardly an expert on international law, nor was I even aware that the Geneva Conventions actually consisted of four distinct treaties and three protocols. However, Article 12 of the Third Geneva Convention seems pretty clear:
Prisoners of war may only be transferred by the Detaining Power to a Power which is a party to the Convention and after the Detaining Power has satisfied itself of the willingness and ability of such transferee Power to apply the Convention. When prisoners of war are transferred under such circumstances, responsibility for the application of the Convention rests on the Power accepting them while they are in its custody.
This article means that if you have captured prisoners of war, you must uphold the Geneva Convention and treat them respectfully according to the Convention. Furthermore, you may not transfer them to another power who you know is not willing to uphold the Convention. For example, handing over prisoners of war to another pwer that tortures prisoners, is nearly as bad as simply torturing them yourself.
If the prisoners detained by the SAS were transferred to the United States at a time when it was generally known that the United States used torture against its prisoners of war, then New Zealand must accept the accusations of the violation of international law (and its consequences). However, I'm not sure that the instances of United States torture were in fact generally known until after the Abu Ghraib events (2004). On this point, the international courts must decide.
These sort of accusations, however, appear to be missing the elephant in the room. The United States now has a fairly well documented portfolio of abusive treatment toward prisoners of war (whether you care to call them "enemy combatants" or any other name). I don't know what the source of these accusations are against New Zealand, but one can only hope that a similar level of scrutiny will also be applied to the United States. It may take decades to resolve, but such abuses cannot remain unpunished.