President George Bush said in his farewell address that "Murdering the innocent to advance an ideology is wrong every time, everywhere." No kidding.
Vincent Bugliosi outlines a possible method for US prosecutors to bring murder charges against the outgoing President, based on existing US law. The legal theory is that 1) he deliberately commenced a war under false pretenses, 2) therefore he deliberately put American soldiers into harm's way, and 3) he is guilty of murdering American soldiers. Sounds far fetched, but Bugliosi is a former LA County District Attorney who won 105 out of 106 cases, and all 21 of his murder trials. It does not matter that he himself didn't kill US soldiers, only that he put them in harm's way. Perhaps this would at least get him convicted for manslaughter.
Other options might be for any country party to the Geneva Conventions to arrest him on travel and charge him there. Singapore is a party to the Conventions and is known to have a rather harsh criminal justice system, so perhaps they might be a good candidate.
George Bush has violated human rights on a massive scale and has permanently tarnished the United States' international reputation. He has not sought forgiveness.