[DugwayDuke]

It is a matter of law, but it is not a matter of criminal law. It is a violation of the laws of Land Warfare, ie, they were illegal combatants. The only court with jurisdiction are military tribunals. IOW, we're doing exactly what is required by international convention, Hague, Geneva, etc.

[JasonC]

They are not parties to such conventions. There is no law between them and us. Lawyers dislike such things, because they remind people they live in the real, natural world, and that the world of law is an entirely artificial second world created only by agreements, among parties that abide by what they agree to. Morality applies quite irrespective of law. But its only support is the hold it has on the actions of just men.