Just recently a sitting officer down in Guantanamo made this exact point when the motion was made related to removing the charges on Omar Khadr because he was a child. He clearly stated the point that the law doesn't define the age of a person who could be before this particular body and used that as one of the cornerstones by which he denied the motion and allowed the trial to move forward.
On May 13th, 2008. See this statement in context.