The conspiracy charge accuses Hamdan of agreeing with al Qaeda to commit murder in violation of the laws of war by transporting two surface-to-air missiles that were to be used against U.S. and allied forces in Afghanistan. In order to find him guilty on that charge, the judge instructed [members], they must find the missiles were intended for use against protected people -- civilians not involved in hostilities, soldiers removed from combat by illness or capture, or religious or medical personnel. The prosecution presented no evidence any such people were targeted. In fact they argued the missiles were intended for use against U.S. forces, who had the only planes in the area. They wanted the judge to revise the instructions and tell [members] that any attempt by an "unlawful enemy combatant" to kill a U.S. soldier in combat is a war crime.
However, after hearing arguments, the prosecution withdrew its objection, reportedly due to the defense's request for a mistrial. Dan Slater at the WSJ Law Blog covers it here.